How do I make 2d movement with strafing?

I'm making a top-down 2d game, where I want the player to be able to strafe/move diagonally. Currently it is kinda working, but not as I want it.

Explanation: When player presses Up, the character moves up. If the player simultaneously presses left, the character moves northwest, facing upwards.

This is what I want to happen, except that I also want this to happen:

Player presses left+up. Character moves northwest, facing left. How can I do so?

Here's my current movement script:

 using UnityEngine;
 using System.Collections;
 
 public class PlayerMovement : MonoBehaviour {
 
     Rigidbody2D rbody;
     Animator anim;
     // Use this for initialization
     void Start () {
     
         rbody = GetComponent<Rigidbody2D> ();
         anim = GetComponent<Animator> ();
     
     }
     
     // Update is called once per frame
     void Update () {
     
         Vector2 movement_vector = new Vector2(Input.GetAxisRaw("Horizontal"), Input.GetAxisRaw("Vertical"));
         
         if(movement_vector != Vector2.zero){
             anim.SetBool("iswalking", true);
             anim.SetFloat ("input_x", movement_vector.x);
             anim.SetFloat ("input_y", movement_vector.y);
         }else{
             anim.SetBool ("iswalking", false);
         }
         
         rbody.MovePosition (rbody.position + movement_vector * Time.deltaTime);
     
     }
 }

And here's the animator: