Title : Tsun na Imouto o Dere Otosu!! Futari de Kurasu Sanjuu Nichi Kan, Make My Tsundere Little Sister Fall for Me!! 30 Days of Living Together, From Tsun to Dere – Conquering Your Sister’s Heart!
Original Title : ツンな妹をデレ堕とす！！ ～二人で暮らす30日間～
Language : Japanese (Official), English (FantL by sutodx)
Developer : Studio Neko Kick
Released date : 2025-05-31, 2025-07-30 (en)

Due to his parents’ sudden trip abroad, the protagonist has to live alone with his rebellious younger sister for a month.
One night, he peeks into his sister’s room and finds her struggling to masturbate for the first time.
As a brother, he decides to develop his sister’s body in the middle of the night in order to release her sexual desire. The naughty 30 days with his sister begins!