Boku Katsu Life: Tomodachi no Otouto-kun to "Game Suru Naka" kara "Cosplay Sex Suru Kankei" ni Naru made

Yuika, a high school girl, became close friends with her friend's younger brother through a shared love of gaming. As they spent more time playing together, she realized he had developed feelings for her.

Though Yuika thought he was too young for a relationship, she wanted to acknowledge his feelings. Their gaming sessions gradually turned into something more intimate, with Yuika helping him with his "needs."

As Yuika became more engaged, her actions escalated, ultimately leading to a "costume play sex" experience!

(Source: Fanza, translated)