
I so confused. What was the game supposed to be and why or how did he even win

Supposedly because Ah-in finally openly admitted that he is not blind (since they were evidently playing this game where both pretended he is blind, despite both of them knowing otherwise).
Though I agree that why or whether that means a win for anyone is a good question. Did Seo win? What did he win? Personally, I actually wonder if Ah-in has the right understanding of it yet - if this even is the sort of game that entails any winning or losing, necessarily.
Omg minhyuk i missed you so much