[pax]

Я бы попробовал так:

using UnityEngine;
using System;
using System.Collections;
using System.IO;

public class filework : MonoBehaviour
{
        void Awake()
        {
                var settingsPath = Application.persistentDataPath+"/Settings/";
                if (!Directory.Exists(settingsPath))
                {
                        Directory.CreateDirectory(settingsPath );
                }
                var iniFile = settingsPath +"settings.ini";
                if (!File.Exists(iniFile))
                {
                        var file = File.Create(iniFile);
                        file.Close();
                        File.AppendAllText(iniFile, "test line 1" + Environment.NewLine);
                        File.AppendAllText(iniFile, "test line 2");
                }
        }
}