WeepingAngel.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[RequireComponent(typeof(VisibleOrNot))]
public class WeepingAngel : MonoBehaviour
{
    private VisibleOrNot _visibleOrNot;

    private void Awake()
    {
        _visibleOrNot = GetComponent<VisibleOrNot>();
    }

    // Use this for initialization
    private void Start()
    {
    }

    // Update is called once per frame
    private void Update()
    {
        if (!_visibleOrNot.IsVisible)
        {
            Vector3 targetDir = Camera.main.transform.position - transform.position;
            float step = .5f * Time.deltaTime;
            Vector3 newDir = Vector3.RotateTowards(transform.forward, targetDir, step, 0.0F);
            transform.rotation = Quaternion.LookRotation(newDir);

            transform.position = Vector3.MoveTowards(transform.position, Camera.main.transform.position, .5f * Time.deltaTime);
        }
    }
}