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 cck 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 cck 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).