Uchi no Ani no Renai Jijou

Overview

Touma lost his parents early in life. The kind-hearted couple who took him in and treated him as one of their own has a son, Tetsuo, whom Touma has come to consider an older brother. But as Tetsuo undergoes a tumultuous - and, ultimately, failed - relationship with an older man, as the normally calm and composed young man breaks down in front of his very eyes, Touma realises that the anguish in his heart is telling him that his feelings for Tetsuo may be very different from brotherly affection. He can never acknowledge this love, for it would be an unspeakable betrayal of his adoptive family. And yet... Could it be that Tetsuo is aware of him? "If you weren't my kid brother, how would you hit on me?" With his every word and action, Tetsuo seems to taunt and tempt Touma.

Source: AniList