Uchi no Otouto Maji de Dekain dakedo Mi ni Konai?

Based on the CG collection by Chinjao Girl. (チンジャオ娘。).

My c*ck is now being seen by my elder sister and two of her friends. "Let's make it bigger!" It was just a joke in the first place but... it ended up with my first sex!? Since then they've been totally into my huge c*ck and come to my house regularly to have sex...

(Source: DLsite English)

Notes:
- A demo was available to the players of RPG browser game Aku no Onna Kanbu: Perigee New Moon (悪の女幹部ペリジーニュームーン) on 2021/03/03.
- Download version was delivered in advance on 2021/04/28, announced on lune-soft's website, and physical version was delivered on 2021/05/28.
- It has live-action AV adaptations: MIMK-066 (2019/02/09) and a remake, MIMK-181 (2025/04/11).