who? yeseong? i think he just guessed at some point. i don't remember if they said at which point exactly he knew
i feel like he knew from close to the beginning. if he's really the kid J saved, as they've been hinting, then he probably had a suspicion from the start and confirmed it pretty quickly with how strong, secretive, and clueless our boi is. XD like posting the stone for auction.
I think he knew from the start, after all Sayoung is the same kind of guy as Hua Cheng. He waited so long for J to return, there is no way that he wouldn't reconize him.
there was a chapter, i think right before J was revealed to still alive and made #1 in rankings, where sayoung was surprised seeing some monster spikes that J had dented. sayoung said something like "i've been looking all over just for him to pop up right next to me" or something?? to me, that showed that he wasn't sure about it, just had a vague feeling or hunch, and seeing the proof of the suspicious part-timer's unique strength was what confirmed it for him. which is why he was already at the incheon memorial site when jung bin rushed over after the rankings were revealed.
oh, sayoung did have an inkling from the moment he saw him but i believe he knew for sure the moment he reappeared on the ranking. yeseong is the one i don't think it's implied when he knew
Honestly some had an inkling he's J cuz all clues led to him but sayoung was pretty much sure about it but they had no proof and it's not like they can just confirm their suspicion out of nowhere
Wait.. When did he found out he's J?