Picked Up By A Younger Boyfriend, Ookamigui

Thirty-ish and gay, Shouta Kogawa has never gotten over his first love. He gets drunk out of his mind and is taken care of by the bursting-with-youth high schooler Mayu Mikuni. He comes to his senses after making an unexpected love confession to Mayu. He won't allow himself to be seduced by a straight teen...

(Source: Fusion Product, translated)

Included one-shot: Ookami Kui