He's in Love with Him.

Synopsis

Toa Mochida, a new employee at Kiryuu Tax Accounting Office, harbors a secret admiration for his boss, Mr. Kiryuu. It all began on a late-night train, where Mochida watched Kiryuu effortlessly diffuse a situation with a drunk passenger harassing a woman, intervening with effortless grace while Mochida himself froze, paralyzed by guilt over his own inaction. Mochida tends to swallow the things he wants to say, but Kiryuu continuously notices, gently offering a hand and watching his back whenever he needs it most. With every quiet gesture, Mochida finds himself falling deeper and deeper...!? (Source: Taiyo Tosho, translated)

Anime adaptations