Because he learned he was a least weasel so he connected the dots that his hair changes in the winter. And also least weasels are rare!
Yeah but its not explicitly shows when he connects the dot right? And like you said the least weasels are rare but what makes him so sure it was him then? He havent seen his winter coat yet
True but they hint at it when Jeongwoo was stressing if he knew and when ML was asking him to search up a least weasel and all that yk? Hope this kinda helped
Wait how did he figure it out it was him? I dont remember he found out about his white fur