SPOILER!!!!!
It's because han is down bad for shinwoo since day one. All his friends know it from the very first start (especially jeonghyeon) and then at some point, han realize that all his exes are just basic on shinwoo appearance... Shinwoo didn't know about this but han and han's friends know that when shinwoo and han lost contact and han have any other lovers, all the lovers are basically just shinwoo's doppelganger xhjdndjsnd ╥﹏╥
Bxjznsk I KNOW RIGHT??!!! But i can't blame shinwoo tho, when even his own family, the person that supposed to be closest to him, treated him like that... No wonder that poor guy got a serious trust issues, deep trauma, and low self esteem ╥﹏╥ he needs to learn about appreciate himself and love himself more so that he can feel the love that other people give him ╥﹏╥
Why does he look like shinwoo so much! Oh lawd I can't handle this, he will only fall deeper into him not thinking he's better off alone, jeez! I know how to fight so he better not come with no foolishness.