Is this story realistic? No.
I can't understand why so many of you are saying that this isn't realistic. Not only I don't need a story to feel realistic to enjoy it, but also I know that just because I've never seen/lived something like this it doesn't mean this stuff doesn't happen. And it's a comedy manga, please treat it as such.
Also, like other people said, I too am really glad that they aren't highschoolers, considering how most yuri manga are set in a highschool.