Sensei no Kanojo

A student experiences her first love with her teacher, finding him strikingly attractive and unlike anyone she has known. Wanting to express her feelings, she attends a gathering with him under a false identity, pretending to be an older student named "Mika." They enjoy the evening, but he firmly rejects any romantic involvement with a student. Despite this, she chooses to see him again, continuing to maintain the deception in order to stay close to him.