Isekai One Turn Kill Nee-sanIsekai One Turn Kill Nee-san ~Ane Douhan no Isekai Seikatsu Hajimemashita~; 異世界ワンターンキル姉さん　～姉同伴の異世界生活はじめました～; 異世界一回殺姐姐 ～姐同伴的異世界生活開始～; 异世界一击无双姐姐~姐同伴异世界生活开启; My One-Hit Kill Sister

You know that one series where the main character gets sent to another world, but his mother gets sent with him, and she’s super overpowered but also really doting to the MC? Yeah, replace “mother” with “big sister” and you have a good idea of what this series is about.