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 March 3rd, 2021.
- Download version was delivered in advance on April 28th, 2021, announced on lune-soft's website, and physical version was delivered on May 28th, 2021.
- A live-action AV adaptation (MIMK-066) was released on February 13th, 2019.