Gokudo-san wa Papa de Aisaika (Kadokawa Ruby Bunko)

[Machine Translation] We're finally having a baby! Sachi, the son and heir to the Amamiya Clinic, receives a bombshell from his childhood friend Kengo, a gangster whom he has no recollection of dating. Due to the circumstances of the child, Fumi's birth, he has no choice but to move in with her to help raise the child! Sachi is perplexed, but for some reason, Kengo is satisfied and treats her like a daughter-in-law. They spend their days like a real family, eating together, taking baths, going to amusement parks, etc. When Sachi nurses Kengo when he catches a cold, Kengo suddenly touches her...?

「ついに俺達の子供ができたぞ!」付き合った覚えもない幼馴染みの極道・賢吾から爆弾発言を受けた雨宮医院の跡取り息子・佐知。連れてこられた子供・史の出生の事情から、やむを得ず子育てを手伝うため同居をすることに!戸惑う佐知を尻目に、なぜか賢吾は満足気に佐知を嫁扱いしてくる。一緒に食事をしたり、お風呂に入ったり、遊園地にでかけたりと本物の家族のように過ごす日々の中、風邪を引いた賢吾を看病する佐知に、急に賢吾が触れてきて...!?