diff --git a/compiler/erg_compiler/codegen.rs b/compiler/erg_compiler/codegen.rs
index 18110790..99ccc400 100644
--- a/compiler/erg_compiler/codegen.rs
+++ b/compiler/erg_compiler/codegen.rs
@@ -1926,9 +1926,10 @@ impl PyCodeGenerator {
                     self.emit_call_local(ident, call.args)
                 }
                 other => {
+                    let is_py_api = other.is_py_api();
                     self.emit_push_null();
                     self.emit_expr(other);
-                    self.emit_args_311(call.args, Name);
+                    self.emit_args_311(call.args, Name, is_py_api);
                 }
             }
         }
@@ -1952,11 +1953,12 @@ impl PyCodeGenerator {
                 Some(8) => self.emit_with_instr_308(args),
                 _ => todo!(),
             },
-            // "pyimport" | "py" |
+            // "pyimport" | "py" are here
             _ => {
+                let is_py_api = local.is_py_api();
                 self.emit_push_null();
                 self.emit_load_name_instr(local);
-                self.emit_args_311(args, Name);
+                self.emit_args_311(args, Name, is_py_api);
             }
         }
     }
@@ -1973,9 +1975,10 @@ impl PyCodeGenerator {
         } else if let Some(func_name) = fake_method_to_func(&class, method_name.inspect()) {
             return self.emit_call_fake_method(obj, func_name, method_name, args);
         }
+        let is_py_api = obj.is_py_api();
         self.emit_expr(obj);
         self.emit_load_method_instr(method_name);
-        self.emit_args_311(args, Method);
+        self.emit_args_311(args, Method, is_py_api);
     }
 
     fn emit_var_args_311(&mut self, pos_len: usize, var_args: &PosArg) {
@@ -2004,7 +2007,7 @@ impl PyCodeGenerator {
         }
     }
 
-    fn emit_args_311(&mut self, mut args: Args, kind: AccessKind) {
+    fn emit_args_311(&mut self, mut args: Args, kind: AccessKind, is_py_api: bool) {
         let argc = args.len();
         let pos_len = args.pos_args.len();
         let mut kws = Vec::with_capacity(args.kw_len());
@@ -2019,7 +2022,12 @@ impl PyCodeGenerator {
             }
         }
         while let Some(arg) = args.try_remove_kw(0) {
-            kws.push(ValueObj::Str(arg.keyword.content.clone()));
+            let kw = if is_py_api {
+                arg.keyword.content
+            } else {
+                Str::from(format!("::{}", arg.keyword.content))
+            };
+            kws.push(ValueObj::Str(kw));
             self.emit_expr(arg.expr);
         }
         let kwsc = if !kws.is_empty() {
@@ -2095,7 +2103,7 @@ impl PyCodeGenerator {
         self.emit_push_null();
         self.emit_load_name_instr(method_name);
         args.insert_pos(0, PosArg::new(obj));
-        self.emit_args_311(args, Name);
+        self.emit_args_311(args, Name, true);
     }
 
     // assert takes 1 or 2 arguments (0: cond, 1: message)
diff --git a/compiler/erg_compiler/context/inquire.rs b/compiler/erg_compiler/context/inquire.rs
index 9078eba4..8cf36caa 100644
--- a/compiler/erg_compiler/context/inquire.rs
+++ b/compiler/erg_compiler/context/inquire.rs
@@ -931,38 +931,25 @@ impl Context {
                 if (params_len < pos_args.len() || params_len < pos_args.len() + kw_args.len())
                     && subr.var_params.is_none()
                 {
-                    return Err(TyCheckErrors::from(TyCheckError::too_many_args_error(
-                        self.cfg.input.clone(),
-                        line!() as usize,
-                        callee.loc(),
-                        &callee.to_string(),
-                        self.caused_by(),
-                        params_len,
-                        pos_args.len(),
-                        kw_args.len(),
-                    )));
+                    return Err(self.gen_too_many_args_error(&callee, subr, pos_args, kw_args));
                 }
                 let mut passed_params = set! {};
-                let non_default_params_len = if attr_name.is_some() && is_method {
-                    subr.non_default_params.len() - 1
+                let non_default_params = if is_method {
+                    let mut non_default_params = subr.non_default_params.iter();
+                    let self_pt = non_default_params.next().unwrap();
+                    if let Err(mut es) =
+                        self.sub_unify(obj.ref_t(), self_pt.typ(), obj.loc(), self_pt.name())
+                    {
+                        errs.append(&mut es);
+                    }
+                    non_default_params
                 } else {
-                    subr.non_default_params.len()
+                    subr.non_default_params.iter()
                 };
+                let non_default_params_len = non_default_params.len();
                 let mut nth = 1;
                 if pos_args.len() >= non_default_params_len {
                     let (non_default_args, var_args) = pos_args.split_at(non_default_params_len);
-                    let non_default_params = if is_method {
-                        let mut non_default_params = subr.non_default_params.iter();
-                        let self_pt = non_default_params.next().unwrap();
-                        if let Err(mut es) =
-                            self.sub_unify(obj.ref_t(), self_pt.typ(), obj.loc(), self_pt.name())
-                        {
-                            errs.append(&mut es);
-                        }
-                        non_default_params
-                    } else {
-                        subr.non_default_params.iter()
-                    };
                     for (nd_arg, nd_param) in non_default_args.iter().zip(non_default_params) {
                         if let Err(mut es) = self.substitute_pos_arg(
                             &callee,
@@ -1010,7 +997,7 @@ impl Context {
                             attr_name,
                             kw_arg,
                             nth,
-                            &subr.default_params,
+                            subr,
                             &mut passed_params,
                         ) {
                             errs.append(&mut es);
@@ -1031,24 +1018,41 @@ impl Context {
                         }
                     }
                 } else {
-                    let missing_len = subr.non_default_params.len() - pos_args.len();
-                    let missing_params = subr
-                        .non_default_params
-                        .iter()
-                        .rev()
-                        .take(missing_len)
-                        .rev()
-                        .map(|pt| pt.name().cloned().unwrap_or(Str::ever("")))
-                        .collect();
-                    return Err(TyCheckErrors::from(TyCheckError::args_missing_error(
-                        self.cfg.input.clone(),
-                        line!() as usize,
-                        callee.loc(),
-                        &callee.to_string(),
-                        self.caused_by(),
-                        missing_len,
-                        missing_params,
-                    )));
+                    // pos_args.len() < non_default_params_len
+                    for kw_arg in kw_args.iter() {
+                        if let Err(mut es) = self.substitute_kw_arg(
+                            &callee,
+                            attr_name,
+                            kw_arg,
+                            nth,
+                            subr,
+                            &mut passed_params,
+                        ) {
+                            errs.append(&mut es);
+                        }
+                        nth += 1;
+                    }
+                    let missing_len = non_default_params_len - pos_args.len() - passed_params.len();
+                    if missing_len > 0 {
+                        let missing_params = subr
+                            .non_default_params
+                            .iter()
+                            .rev()
+                            .take(missing_len)
+                            .rev()
+                            .map(|pt| pt.name().cloned().unwrap_or(Str::ever("")))
+                            .filter(|pt| !passed_params.contains(pt))
+                            .collect();
+                        return Err(TyCheckErrors::from(TyCheckError::args_missing_error(
+                            self.cfg.input.clone(),
+                            line!() as usize,
+                            callee.loc(),
+                            &callee.to_string(),
+                            self.caused_by(),
+                            missing_len,
+                            missing_params,
+                        )));
+                    }
                 }
                 if errs.is_empty() {
                     Ok(())
@@ -1088,6 +1092,76 @@ impl Context {
         }
     }
 
+    fn gen_too_many_args_error(
+        &self,
+        callee: &hir::Expr,
+        subr_ty: &SubrType,
+        pos_args: &[hir::PosArg],
+        kw_args: &[hir::KwArg],
+    ) -> TyCheckErrors {
+        let mut unknown_args = vec![];
+        let mut passed_args: Vec<&hir::KwArg> = vec![];
+        let mut duplicated_args = vec![];
+        for kw_arg in kw_args.iter() {
+            if subr_ty
+                .non_default_params
+                .iter()
+                .all(|pt| pt.name() != Some(kw_arg.keyword.inspect()))
+                && subr_ty
+                    .var_params
+                    .as_ref()
+                    .map(|pt| pt.name() != Some(kw_arg.keyword.inspect()))
+                    .unwrap_or(true)
+                && subr_ty
+                    .default_params
+                    .iter()
+                    .all(|pt| pt.name() != Some(kw_arg.keyword.inspect()))
+            {
+                unknown_args.push(kw_arg);
+            }
+            if passed_args.iter().any(|a| a.keyword == kw_arg.keyword) {
+                duplicated_args.push(kw_arg);
+            } else {
+                passed_args.push(kw_arg);
+            }
+        }
+        if unknown_args.is_empty() && duplicated_args.is_empty() {
+            let params_len = subr_ty.non_default_params.len() + subr_ty.default_params.len();
+            TyCheckErrors::from(TyCheckError::too_many_args_error(
+                self.cfg.input.clone(),
+                line!() as usize,
+                callee.loc(),
+                &callee.to_string(),
+                self.caused_by(),
+                params_len,
+                pos_args.len(),
+                kw_args.len(),
+            ))
+        } else {
+            let unknown_arg_errors = unknown_args.into_iter().map(|arg| {
+                TyCheckError::unexpected_kw_arg_error(
+                    self.cfg.input.clone(),
+                    line!() as usize,
+                    arg.loc(),
+                    &callee.to_string(),
+                    self.caused_by(),
+                    arg.keyword.inspect(),
+                )
+            });
+            let duplicated_arg_errors = duplicated_args.into_iter().map(|arg| {
+                TyCheckError::multiple_args_error(
+                    self.cfg.input.clone(),
+                    line!() as usize,
+                    arg.loc(),
+                    &callee.to_string(),
+                    self.caused_by(),
+                    arg.keyword.inspect(),
+                )
+            });
+            unknown_arg_errors.chain(duplicated_arg_errors).collect()
+        }
+    }
+
     fn substitute_pos_arg(
         &self,
         callee: &hir::Expr,
@@ -1190,7 +1264,7 @@ impl Context {
         attr_name: &Option<Identifier>,
         arg: &hir::KwArg,
         nth: usize,
-        default_params: &[ParamTy],
+        subr_ty: &SubrType,
         passed_params: &mut Set<Str>,
     ) -> TyCheckResult<()> {
         let arg_t = arg.expr.ref_t();
@@ -1207,8 +1281,10 @@ impl Context {
         } else {
             passed_params.insert(kw_name.clone());
         }
-        if let Some(pt) = default_params
+        if let Some(pt) = subr_ty
+            .non_default_params
             .iter()
+            .chain(subr_ty.default_params.iter())
             .find(|pt| pt.name().unwrap() == kw_name)
         {
             self.sub_unify(arg_t, pt.typ(), arg.loc(), Some(kw_name))
@@ -1263,7 +1339,6 @@ impl Context {
     ) -> TyCheckResult<VarInfo> {
         if let hir::Expr::Accessor(hir::Accessor::Ident(local)) = obj {
             if local.vis().is_private() {
-                #[allow(clippy::single_match)]
                 match &local.inspect()[..] {
                     "match" => {
                         return self.get_match_call_t(SubrKind::Func, pos_args, kw_args);
@@ -1271,20 +1346,6 @@ impl Context {
                     "match!" => {
                         return self.get_match_call_t(SubrKind::Proc, pos_args, kw_args);
                     }
-                    /*"import" | "pyimport" | "py" => {
-                        return self.get_import_call_t(pos_args, kw_args);
-                    }*/
-                    // handle assert casting
-                    /*"assert" => {
-                        if let Some(arg) = pos_args.first() {
-                            match &arg.expr {
-                                hir::Expr::BinOp(bin) if bin.op.is(TokenKind::InOp) && bin.rhs.ref_t() == &Type => {
-                                    let t = self.eval_const_expr(bin.lhs.as_ref(), None)?.as_type().unwrap();
-                                }
-                                _ => {}
-                            }
-                        }
-                    },*/
                     _ => {}
                 }
             }
diff --git a/compiler/erg_compiler/hir.rs b/compiler/erg_compiler/hir.rs
index 83874345..1f5a37ef 100644
--- a/compiler/erg_compiler/hir.rs
+++ b/compiler/erg_compiler/hir.rs
@@ -422,6 +422,10 @@ impl Identifier {
         Self::new(dot, name, None, VarInfo::const_default())
     }
 
+    pub fn is_py_api(&self) -> bool {
+        self.vi.py_name.is_some()
+    }
+
     pub fn is_const(&self) -> bool {
         self.name.is_const()
     }
@@ -539,6 +543,13 @@ impl Accessor {
         }
     }
 
+    pub fn is_py_api(&self) -> bool {
+        match self {
+            Self::Ident(ident) => ident.is_py_api(),
+            Self::Attr(attr) => attr.ident.is_py_api(),
+        }
+    }
+
     // 参照するオブジェクト自体が持っている固有の名前(クラス、モジュールなど)
     pub fn qual_name(&self) -> Option<&str> {
         match self {
@@ -1919,6 +1930,13 @@ impl Expr {
         }
     }
 
+    pub fn is_py_api(&self) -> bool {
+        match self {
+            Expr::Accessor(acc) => acc.is_py_api(),
+            _ => false,
+        }
+    }
+
     pub fn is_type_asc(&self) -> bool {
         matches!(self, Expr::TypeAsc(_))
     }
diff --git a/compiler/erg_compiler/ownercheck.rs b/compiler/erg_compiler/ownercheck.rs
index 872bfb60..f53266de 100644
--- a/compiler/erg_compiler/ownercheck.rs
+++ b/compiler/erg_compiler/ownercheck.rs
@@ -136,20 +136,23 @@ impl OwnershipChecker {
                 } else {
                     args_owns.non_defaults.len()
                 };
-                let (non_default_args, var_args) = call.args.pos_args.split_at(non_defaults_len);
-                for (nd_arg, ownership) in
-                    non_default_args.iter().zip(args_owns.non_defaults.iter())
-                {
-                    self.check_expr(&nd_arg.expr, *ownership, false);
-                }
-                if let Some(ownership) = args_owns.var_params.as_ref() {
-                    for var_arg in var_args.iter() {
-                        self.check_expr(&var_arg.expr, *ownership, false);
+                if call.args.pos_args.len() > non_defaults_len {
+                    let (non_default_args, var_args) =
+                        call.args.pos_args.split_at(non_defaults_len);
+                    for (nd_arg, (_, ownership)) in
+                        non_default_args.iter().zip(args_owns.non_defaults.iter())
+                    {
+                        self.check_expr(&nd_arg.expr, *ownership, false);
                     }
-                } else {
-                    let kw_args = var_args;
-                    for (arg, (_, ownership)) in kw_args.iter().zip(args_owns.defaults.iter()) {
-                        self.check_expr(&arg.expr, *ownership, false);
+                    if let Some((_, ownership)) = args_owns.var_params.as_ref() {
+                        for var_arg in var_args.iter() {
+                            self.check_expr(&var_arg.expr, *ownership, false);
+                        }
+                    } else {
+                        let kw_args = var_args;
+                        for (arg, (_, ownership)) in kw_args.iter().zip(args_owns.defaults.iter()) {
+                            self.check_expr(&arg.expr, *ownership, false);
+                        }
                     }
                 }
                 for kw_arg in call.args.kw_args.iter() {
@@ -159,6 +162,12 @@ impl OwnershipChecker {
                         .find(|(k, _)| k == kw_arg.keyword.inspect())
                     {
                         self.check_expr(&kw_arg.expr, *ownership, false);
+                    } else if let Some((_, ownership)) = args_owns
+                        .non_defaults
+                        .iter()
+                        .find(|(k, _)| k.as_ref() == Some(kw_arg.keyword.inspect()))
+                    {
+                        self.check_expr(&kw_arg.expr, *ownership, false);
                     } else {
                         todo!()
                     }
diff --git a/compiler/erg_compiler/transpile.rs b/compiler/erg_compiler/transpile.rs
index 0c634938..d6120ec3 100644
--- a/compiler/erg_compiler/transpile.rs
+++ b/compiler/erg_compiler/transpile.rs
@@ -431,6 +431,7 @@ impl ScriptGenerator {
     }
 
     fn transpile_simple_call(&mut self, mut call: Call) -> String {
+        let is_py_api = call.obj.is_py_api();
         let mut code = format!("({})", self.transpile_expr(*call.obj));
         if let Some(attr) = call.attr_name {
             code += &format!(".{}", Self::transpile_ident(attr));
@@ -441,7 +442,12 @@ impl ScriptGenerator {
             code.push(',');
         }
         while let Some(arg) = call.args.try_remove_kw(0) {
-            code += &format!("{}={},", arg.keyword, self.transpile_expr(arg.expr));
+            let escape = if is_py_api { "" } else { "__" };
+            code += &format!(
+                "{}{escape}={},",
+                arg.keyword.content,
+                self.transpile_expr(arg.expr)
+            );
         }
         code.push(')');
         code
diff --git a/compiler/erg_compiler/ty/mod.rs b/compiler/erg_compiler/ty/mod.rs
index 09817a6e..2e729db0 100644
--- a/compiler/erg_compiler/ty/mod.rs
+++ b/compiler/erg_compiler/ty/mod.rs
@@ -882,22 +882,26 @@ impl Ownership {
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct ArgsOwnership {
-    pub non_defaults: Vec<Ownership>,
-    pub var_params: Option<Ownership>,
+    pub non_defaults: Vec<(Option<Str>, Ownership)>,
+    pub var_params: Option<(Str, Ownership)>,
     pub defaults: Vec<(Str, Ownership)>,
 }
 
 impl fmt::Display for ArgsOwnership {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "(")?;
-        for (i, o) in self.non_defaults.iter().enumerate() {
+        for (i, (name, o)) in self.non_defaults.iter().enumerate() {
             if i != 0 {
                 write!(f, ", ")?;
             }
-            write!(f, "{o:?}")?;
+            if let Some(name) = name {
+                write!(f, "{name}: {o:?}")?;
+            } else {
+                write!(f, "{o:?}")?;
+            }
         }
-        if let Some(o) = self.var_params.as_ref() {
-            write!(f, ", ...{o:?}")?;
+        if let Some((name, o)) = self.var_params.as_ref() {
+            write!(f, ", ...{name}: {o:?}")?;
         }
         for (name, o) in self.defaults.iter() {
             write!(f, ", {name} := {o:?}")?;
@@ -909,8 +913,8 @@ impl fmt::Display for ArgsOwnership {
 
 impl ArgsOwnership {
     pub const fn new(
-        non_defaults: Vec<Ownership>,
-        var_params: Option<Ownership>,
+        non_defaults: Vec<(Option<Str>, Ownership)>,
+        var_params: Option<(Str, Ownership)>,
         defaults: Vec<(Str, Ownership)>,
     ) -> Self {
         Self {
@@ -1678,9 +1682,12 @@ impl Type {
                         Self::RefMut { .. } => Ownership::RefMut,
                         _ => Ownership::Owned,
                     };
-                    nd_args.push(ownership);
+                    nd_args.push((nd_param.name().cloned(), ownership));
                 }
-                let var_args = subr.var_params.as_ref().map(|t| t.typ().ownership());
+                let var_args = subr
+                    .var_params
+                    .as_ref()
+                    .map(|t| (t.name().unwrap().clone(), t.typ().ownership()));
                 let mut d_args = vec![];
                 for d_param in subr.default_params.iter() {
                     let ownership = match d_param.typ() {