Manazashi no Hayagane by Kakine [Eng]

Manga Summary:

Eri has always been careful to hide his true self. However, fate takes an unexpected turn when one of the new teaching assistants under his supervision turns out to be Motou—an old student from his past. Confronted by Motou’s sincere gaze, Eri struggles to maintain his facade. Thus begins a years-spanning romance between a devoted teaching assistant and a teacher who wears a mask.

Meanwhile, at the same school, love begins to blossom between Motou’s hardworking friend, Izumi, and Makino, a socially awkward cram school teacher. Their story unfolds in “Together.”