Saeki, who started a delivery part-time job two months ago, is intrigued by a customer named Yuki, to whom he delivers packages about twice a week. Not only is Yuki a giant, timid hikikomori... but it seems he has a crush on Saeki. However, Saeki, who is gay, prefers "slender, small, and cute boys." He felt no attraction whatsoever to Yuki, who is the complete opposite of his type—but one day, he accidentally catches Yuki masturbating in his room, moaning Saeki's name in ecstasy...!? A size-difference love story that flips sexual preferences upside down, featuring a secretly sadistic delivery worker × a super masochistic body with a natural sweet personality ♡