My One-Hit Kill Sister - S01

While saving a child from danger, the otaku Asahi Ikusaba is sent to another world and thinks he has reincarnated with cheat skills like the ones in his favorite games and novels. But reality hits when he runs into a powerful monster and learns he is still just an ordinary person. In that moment of extreme danger, Asahi instinctively calls out to his doting sister, Maya, who appears out of nowhere with the overpowered abilities he thought he had. Maya is thrilled to see her brother again and decides to use her new powers to protect Asahi no matter what. Together, the close siblings try to find a way home while enjoying their new lives. But it soon becomes clear that their arrival in this world may have had a purpose. With the Demon King's overwhelmingly powerful army approaching, no one but Maya seems able to stand in its way.