How to move direction of particle(s) emitted by ParticleSystem Shuriken

It's more easy if you create a prefab.

and use this code in your player

 var shuriken : GameObject;
 var throwShuriken = false;
 var throwShurikenTime : float = 0;
 var throwShurikenNumber : float = 0;
 
 function Update()
 ///key pressed {throwShuriken=true;}
 if(throwShuriken){
 throwShurikenTime + = Time.deltaTime;
 if(throwShurikenTime>=0.5){
 throwShurikenNumber +=1;
 clone = Instantiate(shuriken, transform.position, transform.rotation);
 if(throwShurikenNumber>=10){
      throwShuriken=false;
 }
 }
 }
 }

to follow you create a script and attach to your shuriken

i'm portuguese "rotacao" it's max rotation that your shuriken can do; and "tempo" is the maximo time that shurikens are on the field;

var target : Transform; var tempo : float =0;

function Update(){ tempo+=Time.deltaTime;

     transform.Translate(Vector3.forward*Time.deltaTime*speed);
     
     if(rotacao>=-40 && rotacao<=40){
     
     var relativePoint = transform.InverseTransformPoint(target.transform.position);
         
     if (relativePoint.x < 0.0){
         transform.Rotate(0, rotacaospeed*-1 , 0);
         rotacao-=rotacaospeed;
     }else if (relativePoint.x > 0.0) {
         transform.Rotate(0, rotacaospeed , 0);
         rotacao+=rotacaospeed;
     }else{
         transform.Rotate(0,0,0);
     }
     }

      if(tempo>=2){
            Destroy(gameObject);
       }

}