Black List

When he was in jr.high, Kuroi Teisuke overheard his friend that he has crush with that she likes people with deep voice, so he plans to confess his love to the girl he likes when he has his voice changes. Unfortunately, even when he's 16 years old but unlike other boys, his voice hasn't change yet. What he should do? And what about mysterious boy and girl that came up to him? Who are they?