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

Asahi Ikusaba is transported to another world following a real-world accident. Expecting to experience a new and exciting environment, he quickly discovers his abilities are among the weakest. During an encounter with a dangerous monster, he is rescued by his older sister, Mayu, who has also arrived in this world. Unlike Asahi, Mayu possesses formidable power and exceptional abilities. She follows Asahi out of affection and ends up in the same world, where her strength becomes evident. The story follows their new life in this fantasy setting, where Mayu's overwhelming skills contrast sharply with Asahi's lack of power.