Studio Sellfish released an anime hentai adaptation of the popular manga "Gaki ni Modotte Yarinaoshi!!! | Turning Back Into a Kid And Starting Over!!!" by Maron Maron. The main character never communicated with or had sexual experience, and in general had absolutely no experience interacting with girls due to a deep psychological trauma from childhood. His beloved Kasumi is about to get married. He is lost and upset. The hero runs wherever his eyes lead him and unexpectedly loses consciousness. He wakes up to a painfully familiar voice - "Boku-kun! Boku-kun!". It was the childhood voice of his beloved little sister Kasumi. Wait! This is indeed Kasumi, and she is still very young... He got a chance to go back in time and become what he always dreamed of being. However, after a short reflection, he realizes he has no time to dream and decides to turn all his lustful dreams into reality...