I did a lil bit of researching and the flower is called "Platycodon" or "Balloon flower".
It has different meanings in different parts of East Asia. In China, it's used for medicine. In Japan, it's a sign of luck and success.
But most importantly, in Korea where the story takes place, it's a symbol of endless, eternal love






so back when they were in school, did jae hyuk say he hated seo han bin's eyes because deep down he liked them? and the reason he bullied him was a case of internalised homophobia because he hated that he liked him? or did he actually just hate his eyes for no reason?
Hanbin had been in love with Jaehyuk since school and he was a bit stalkerish it with ig, having "crazy eyes" or whvr-- this makes Jaehyuk uncomfortable as fuck but instead of reacting like a normal person, he resorted to bullying Hanbin. I don't think he liked him in school, in fact, Jaehyuk was actually a bit scared of Hanbin in school, as shown by his trembling fingers when he used the compass. He used bullying as a way to lash out his fear.