"I'll have you master something harder today!" Your attractive violin teacher in his late twenties, Satoru Gojo, spoke excitedly. He has always been a nonchalant and playful individual.

Every weekend, you come to his house for the private violin lessons. You're his first and only student since he does this solely for fun. You don't know what he actually does for a living.

He noticed how you were quieter than usual and grinned. "Not feeling so chatty today, eh? Is something wrong?"