Muv-Luv Substance

Muv-Luv Substance (マブラブ・サブスタンス), stylised Sub Stance, is a free doujin, three-part spin-off/parody, game to the original Muv-Luv, and was released in 2005.

The premise is that Takeru, who has experienced both Extra and Unlimited world lines, wakes up in a parallel world that is exactly the same as Extra. However, this new world is fatally different, nicknamed Substance. Once again, reality mercilessly invites him to adventure, and to seek out his original world. After meeting with Kouzuki Yuuko, he must await X-Day, and survive the tomboyish heroine(s) standing in his way.