Responses
For making him a rebound*, he IS a rebound and that's why Jun is so stressed at the end. That's why Subin is toxic for Jun. Those aren't just Jun's insecurities, Subin very obviously hasn't gotten over Hyunwoo, he's settling.
You take the word "toxic" and run with it.
One more, educate yourself on how to use the word rebound in this context because that's an embarrassing take.
Subin's decisions made a lot of things difficult for everyone. Hyunwoo has his own faults too. Jun seems to be the only person who consistently got his shit together and I'm glad he told off Subin for trying to make him a rebound.