It's a very small game about brother and sister going to the lewd dungeon together, with a decision to fuck or not to fuck your sister left to you. Endings are sparse (you can do weird stuff like magically impregnating your sister without deflowering her, or sleep-raping her without her knowing, but that is not reflected in the ending text), but that's probably the only downside. Worth two or three playthroughs (a gentleman one, a pervert one and the one where you're trying to do weird stuff) which together will take less that an hour. There are cute prequels/backstories that are genuinely interesting. The tiny scope of this game is it's main advantage, it's good at what it does.