Isshinjou no Tsugou ni yori, Mukoyoushi wa Hajimemashita.

Overview

Miyajima, a secretly gay man, is the heir to a high-class ryotei (Japanese-style restaurant). He has a secret crush on his childhood friend Takeuchi, a handsome and taciturn chef. Feeling self-conscious about his homosexuality, he has lived his whole life in the closet, both with Takeuchi and with his parents, until one day when his father, the head chef, suddenly collapses. Miyajima decides to return home to the restaurant, only to find Takeuchi has unexpected been adopted as the new "son-in-law"—! (Source: Gush, translated)

Source: AniList