Ojisan to Ore no Koiwazurai

Since Kaname was a young boy, he's shared a secret with his uncle Takashi: That both of them are gay. He takes it upon himself to cheer his uncle up whenever his heart gets broken. Though after not seeing him for ten years, Kaname seems to have fallen right back into this role. Except, only one thing has changed...his feelings. He comforts his uncle so many times, but after his feelings build up, Kaname can't hold back any longer.

"Let me stand in for them."

(Source: Sankosha, translated)