mmorpg2d/Assets/Script/NpcUI.cs

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

public class NpcUI : MonoBehaviour
{
    public Button btnNext;
    public void Start(){
        btnNext.onClick.AddListener(onNext);
    }

    void onNext(){
        npcScript.activeNpc.NextLine();
    }
}