Dear Self-styled F rank bro' says, he's gonna rule a game-oriented school.

Story:

Shishio Academy is a prestigious, the best school in Japan, in which only the elite of such fields as study, sports, pedigree can study. But in reality it is a school of principles of “devouring the weak by the strong”, where everything is measured by the results of the games. This is a massacre in which only a definite winner can survive. Guren is a legend of the shadow world, conquering and invincible, and at the same time he wants to start a normal, carefree life. He fails the entrance exams to the academy on purpose, therefore, following his results, he qualifies as the lowest grade F. However, after reuniting with his younger sister Karen, the situation changes dramatically. And when his sister is in danger, he shows his true abilities!