Responses

You're right. The flashback doesnt show the whole thing. At least we have those pic and text message that shows how close they were in the past (ps idk if the text the lovey dovey one or just a close chat between close fr)
Well this is just my opinion. I think the author show us two different flashback. One when they just got close as sunbae and hoobae, and second after the fire accident which mean right now. That will be more make sense
Wasn't Sihoo diagnosed to have amnesia and forgets every happy memories? Even Taehyuk confirmed that. If he had completely forgotten Yesung, wouldn't it'd be alright to assume that Yesung had been a subject for his happy memories?
Then again, they we're still sunbae and hoobae with the rumors. But the flashbacks are still incomplete. In addition to that, if they were still in a sunbae-hoobae relationship, then why would Sihoo forget about Yesung when they met in a cafe? When the fire already happened then. Wouldn't it be more reasonable that Sihoo remembered Yesung as a sunbae rather than his bf then since the fire is a trigger that lets him forget happy memories?
One thing that also gives me doubts is Sihoo's feelings for Yesung when they met. It was out of pure curiosity, and when he was told they were lovers there was confusion. Not the cliché stuff that he just felt right then. But then he easily is attracted to Yesung and is very comfortable with him, as if he is home or his anchor (when his headache stopped when Yesung visited him) and it's all up to creator anyway. Looking forward for more flashbacks for answers.