He is the boy that Arata Kohata confessed her feelings for, and is apparently in the third class.
He seems to be a somewhat meek person and also seems to have been forced by the other boys to put up Arata's love letter so that she could become the laughingstock of the school. Takuu really does care about Arata's feelings, as he shows his affections toward her in episode 4 of the anime series.
He and Arata became a couple in the final episode after regaining her feelings for him. Of course, Mato comes in to ruin the moment.