シーン読んだ後にリソースを読む

Load.cs

using UnityEngine;
using System.Collections;
using UnityEngine.SceneManagement;

public class Load : MonoBehaviour {

	IEnumerator Start () 
	{
		// ステージを読む
		var stageAB = AssetBundle.LoadFromFile (Application.streamingAssetsPath + "/stage");
		SceneManager.LoadScene ("stage", LoadSceneMode.Additive);

		// モデルデータやテクスチャを非同期でロード
		var modelABResult = AssetBundle.LoadFromFileAsync (Application.streamingAssetsPath + "/ball");
		yield return new WaitWhile (() => modelABResult.isDone == false);

		// missingな設定を再設定
		var gimic = GameObject.Find ("Gimic");
		gimic.SetActive (false);
		gimic.SetActive (true);

		// 依存の解決に1F何故か必要
		yield return null;
		// AssetBundleを解放
		modelABResult.assetBundle.Unload (false);
		stageAB.Unload (false);
	}

}