Jishou F-Rank no Oniisama ga Game de Hyouka sareru Gakuen no Chouten ni Kunrin suru Sou desu yo?

Shishio Academy is a school where everything is decided upon by the results of games. During the entrance exams, Guren ended up with the worst rank: The F-rank, just as he had planned. But once the academy's 'darkness' begins to attack his beloved little sister Karen, Guren has to show his true skill!