It Seems I Was Hitting on the Most Beautiful Girl in School Without Me Noticing summary:
The protagonist begins to get involved with the most beautiful girl in school, who is famous for her cold attitude, and slowly becomes attracted to her.
That protagonist finds himself in a consulting relationship with a plain girl in glasses at his part-time job.
He doesn’t realize that the girl he is consulting is the same girl he is in love with, and just keeps telling her about his growing feelings while continuing to fall in love with her.
The heroine realizes that the person he is in love with is herself, and although she is embarrassed by the protagonist’ feelings, she gradually becomes attracted to him.