And he was covered in poison and after that all bandaged up.
and bc sayoung knows that it was J that saved him and he also found out that Uijae was J therefore figuring out that Uijae was the one who saved him
well Lee sayoung was a hurt kid the first time they met, spoke once barely while asking for help, then got wholly bandaged for a long time. He couldn't speak then, and J was more worried about his physical condition than focusing on recognizing him 8 years after. He could also never guess that sick kid would be so healthy afterwards, specially since he was not an awakened before.
Add on to other comments, who would've imagined said sick kid to become one of the major guilds leader in Korea? Lol
Well, he was covered in poison and now he's toxic so it was logical for me. But, you're right, who would've imagine him to become so important figure.
So Sayoung knows that IT was J who saved him. Why J doesn't figure IT out himself? Maybe because Sayoung doesn't look do young?