I can't understand that "Stay away!" line and slapping her hand away. Isn't that something you'd do to a stranger or half-stranger that suddenly tried to stick to you and touch you?
Bros taking the role of the girl in clichee ecchi stories going "kyaaaa, hentai" lmao.
That aside, the sister also has no room to talk, shes sabotaged this relationship multiple times already.
That slap was ridiculous... Akkun needs to apologize asap..she's a friend and love interest so you should be able to handle accidents like that accidental flash.