I'd like to move a cube without delay.(C#)

Hello, guys.

(I'm not good at English well. Please understand me.)

Now I'm studying about moving a cube. I found one way to do this with StartCoroutine() and yield return new WaitForSeconds() codes. But I'd like to know there is another way to move a cube. The most important thing for me is 'No delay'. If there is a way to move a cube without delay(except count seconds), please teach me. Below is my code. Thanks!!

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 using UnityEngine;
 using System.Collections;
 
 public class Manager : MonoBehaviour {
     
     public int state=0;
     
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
     
     switch(state) // state = 4 -> wait
         {        
         case 0:
             StartCoroutine(forward());
             break;
         case 1:
             StartCoroutine(backward());
             break;
         case 2:
             StartCoroutine(left());
             break;
         case 3:
             StartCoroutine(right());
             break;
         default:
             break;
         }
     }    
     
     public IEnumerator forward()
     {
         state = 4;
         iTween.MoveTo(GameObject.Find("Cube").gameObject, iTween.Hash( "y", 1, "easeType", iTween.EaseType.easeInOutSine));
         yield return new WaitForSeconds(2.0f);        
         state = 1;        
     }
     
     public IEnumerator backward()
     {
         state = 4;
         iTween.MoveTo(GameObject.Find("Cube").gameObject, iTween.Hash( "y", -1, "easeType", iTween.EaseType.easeInOutSine)); 
         yield return new WaitForSeconds(2.0f);
         state = 2;
     }
     public IEnumerator left()
     {
         state = 4;
         iTween.MoveTo(GameObject.Find("Cube").gameObject, iTween.Hash( "z", 1, "easeType", iTween.EaseType.easeInOutSine)); 
         yield return new WaitForSeconds(2.0f);
         state = 3;
     }
     public IEnumerator right()
     {
         state = 4;        
         iTween.MoveTo(GameObject.Find("Cube").gameObject, iTween.Hash( "z", -1, "easeType", iTween.EaseType.easeInOutSine)); 
         yield return new WaitForSeconds(2.0f);        
         state = 0;
     }    
 }
 
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