I feel like it was when he made the cookies for him and then he sent a picture of them to jistar stating his neighbor made him cookies
Yeowoon never sent the pictures to Jistar, only to his two friends. Jigu most likely suspected Yeowoon when Yeowoon told Jigu about the madeleines, then confirmed it when Yeowoon went over to Jigu's place and Yeowoon got the text the exact same time Jigu had texted him.
I must’ve got it mixed up then . Cause I swear he told jistar bout them cookies
How tf did jigu find out that yeowoon is neutaaaa first