Oh boy…
Relationship wise? Eh. character wise… yeah like a lot
How???
Yeonwoo actually changed and gained a lot of confidence after many struggles. He also resolved his issues with Junhyuk. As for Junhyuk, his character is further developed by flashbacks and his encounter with him and Yeonwoo's long time bully. Im Nari is just a plot device tbh. We don't know much about Haseol but her back story is hinted at in the latest chapters.
Ahh tyyy
Came back after a couple years and omg has anything happened in that time??