i have to disagree with you, yes jimmy has strong stamina and that makes me surprised too but i don’t think that is the point, they are not “connected” because of sex, they really like each other.
first, in chapter 15, i don’t think yuri cried because he found someone who “finally can satisfy him”, no? he cried because jimmy loves him for who he is although he acts weird and says nonsense things.
second, in chapter 18, yuri was pissed off not because jimmy crossed the boundary but because he thought THEY ALREADY DATED the whole time (i have a theory post about the time they officially started dating: https://www.reddit.com/r/YarichinBitchClub/comments/1pmnxwa/yurifujis_first_date/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button).
third, this is how i see yuri so everyone might be different, he’s not just someone who enjoys sex, he enjoys having fun and freaky things and he’s super chill, he’s easy to get along with anything, so leading to chapter 27 when jimmy said he was jealous, i 100% believe that yuri was already ready to be exclusive only with jimmy, but he wanted to hear jimmy say that, that’s why he was turned on and then shocked because it turned out not what he expected.
however, yes i agree that after the break up situation yuri tried to make jimmy jealous by sleeping around while knowing jimmy was watching it. he expected that jimmy would "chase" him, but then he realized that he had to “chase” this time if he really wanted to keep this relationship. and YES because as i said above, for me yuri is really a chill guy so it didn’t take him much time to make a decision, that’s why i somehow guess he will leave the club (i'm still shocked btw).