SV, Koi no Shinchoku ni Tsuite.

Yonemura, a supervisor of a convenience store, and his boyfriend Andou, a cheeky part-timer who's over ten years younger, are not in an intimate relationship yet. But soon, Andou will celebrate his 20th birthday, so Yonemura is secretly planning something. Due to Yonemura's busy schedule, they can barely see each other. Then enters Mitsuhara, a new part-timer who can't seem to control his hands around Yonemura. Problems start to rise between the three!

(Source: Kadokawa, translated)