Searching for a shoujo / josei manga

So i read this years ago and the story is about a girl in college that everyone think is mature but she's actually a bit childish and her childhood friend who's the opposite he's secretly a genius a bit of a yandere . College is not a big part of the manga and i remember her having brown/red hair and him blond. There is a scene where she put ice in her tea because she can’t wait for it to cool and another where they go to a love hotel because she's sick or something . Please help me find it .