"Please let me take responsibility!"

Rui, a pharmacist, is a pleasure-seeker who aggressively pursues sexual conquests. One day, he picks up a drunken virgin boy, Takanashi, from a bar he frequents. They have great physical chemistry together, but as usual, Rui leaves the hotel thinking it will be a one-night stand. However, to his surprise, Takanashi begins to fiercely pursue him, telling him "I think I've fallen in love with you, Rui-san." He joins Rui's workplace as a part-time worker and follows his every move, acting almost like a stalker, which is a little off-putting at first. But Rui's heart is gradually shaken by Takanashi and his earnest attitude...?

(Source: Kaiohsha, translated)