From Shinmakoku Scanlations :

This is a spin-off to Tenchou, Koi desu.

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