Due to the overwhelming success of I Hear the Sunspot, the sequel has finally arrived, I Hear the Sunspot: Theory of Happiness! How will this "more than friends, less than lovers" relationship evolve?
—he can't hear . . . ?
Because of a hearing disability Kohei is often alone. Taichi is outspoken and cheerful. At first, Kohei keeps himself well guarded, but after he meets Taichi he slowly learns to open up.