Okay, im just geussing here.. So, when he interviewed his sister he must of had a card that includes her info... Why? Well because its work.. Perhaps while looking at her info he sees the last name is similar making both uke the girl related...
Guess number 2....in previous episodes they would always go out to a cafe and the seme probably got used to his uke's preferences..
i reread the chp and he always ordered hot americano for him LMAO he sus
Welp we never know ╮(￣▽￣)╭
he ordered iced americano for him.... damn he is so mysterious....