Isekai One Turn Kill Nee-san: Ane Douhan no Isekai Seikatsu Hajimemashita

The story follows Asahi Ikusaba, a high-school student who got lost and ended up in another world. He has knowledge of video games and fantasy worlds, but he is weak and does not have any "cheat abilities." He finds his older sister Mayu in the other world, and she has the strongest cheat ability and also has a brother complex.