The user is able to hear a film score of music in the background of any situation they are in. The score matches the tone of the situation: happy music for a carefree scenario, and dreading music in a suspenseful situation. The user is the only person who can hear this score.

SO how is this useful? Well, have you ever watched a horror film and thought 'run away, the music is swelling, the killer is obviously hiding behind the door!'? Well, now you can basically be that character and follow that advice! You might be walking around, going about your day when all of a sudden the score becomes loud and intense. You will infer that there is a threat nearby and go on guard.

Another application is as a lie detector. The user might ask a question, and when the target responds the music will either grow suspenseful or chill depending on whether they are lying.

I imagine this ability belonging to an unconscious nen genius like komugi, but someone who is just really into movies.