Something people seem to be missing: When Yuu asked of her senpai had ever been excited by someone's confession before, she prefaced her question by saying "leaving aside girls". It's perfectly possible that she's a lesbian and rejected the confessions she got from other girls for various reasons beyond her sexuality (didn't think they were serious, still in the closet, her reputation).
On an unrelated note: Am I the only one who's moderately worried by the title?