from someone who read the manga that came before this one, i think that this is a perfect example of seeing two sides of the story.
from the pov of shimada, he didn’t know about daichi’s ordeal with loving the manager. he doesn’t know how daichi is trying his best to move on from it, or that what daichi has is a more complex love and not just a crush. another thing to point out is that makoto gave this information to shimada as if it was a light topic, and that bringing it up is no biggie. also at that time, shimada was feeling pressured to voice out that he loves takeru, since it has always been takeru showing his love.
then we see daichi’s pov here which shows us that his love for the manager is actually something that burdens him. the only people so far who knows about it are tamotsu and the more experienced member in the club. if you only read the first manga it really looked like daichi was trying to snatch takeru, but in here we see that he just wants to take his mind off of things hence he was talking so fondly towards takeru, and his teasing are just from him relieving stress.
so no none of them are in the wrong. don’t make it as if shima intentionally wanted to embarrass daichi.
When a I read the 07, I was like, maybe Daichi is saying like "If you don't fu*k that guy, I wanna it", maybe I'm mistaking or I got confused (sometimes I really don't know who is whom), but I really didn't saw Daichi going after him... And shimada just blew everything up... And don't come with the "he was drunk"... I don't give a damn, he just destroyed Daichi faced...