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).