Why did I have to come home so early if you were just sleeping?
寝てるんだったら何のために早く帰ってきたかわからないよ。
=なんで早く帰らなければいかなかったの?
You told me that you would stay awake until I am back.
俺が返ってくるまで起きてるって言ってたじゃん。
That's why I came home so early today.
だからこんなに早く帰ってきたんだよ!
But I was lucky to see your adorable sleeping face.
だけどかわいい寝顔が見れたのはラッキーだったぜ。