Kkay this is major spoiler.
The flashback arc will start when that lady-relative of YS (i forgot her name ) tells the whole story to HY and she literally lowkey blaming like “do you still want him to choose you evn if all that youve caused him was pain and suffering? Dont u have ur conscience?” Something like that. HY realizes he wants to put an end to YS’s suffering by telling him the truth, their story, so that they can let each other go only for YS to declare that he knows everything. Then they had sex. (▰˘◡˘▰) they took their time afterwards. U rmmbr that one time in the past where YS said to HY that whatever season, however long he’d have to wait, he’d wait for HY’s answer? He tells HY the same thing now theyre together. That if HYs still doubting and still afraid, hell continue to wait. i hope this makes your day. YS’s accident arc is rly tragic tho.
That was a trap YS set to catch HY so he can have solid evidence of HY being part of his life years ago. YS knows that if he just hastily tells HY he remembers everything in the past, HY will just run away again . HY picking up that ring from the bin later in the story will be YS’s solid evidence. (▰˘◡˘▰)