re-read 25.12.2020
First couple are a 3rd year high school student and his Japanese teacher. They have an HEA.
Second couple is a young university part-timer who notices his sempai at work having an unrequited love towards his high school friend, and seduces him away by using the same cologne the friend used to wear. I think they have a HEA too, after the older sempai gets over his broken heart.
Third couple are about two men who were lovers in high school, and never got over it, meeting again when it’s ”too late” for the both of them.
Yukidoke no Koi