Pocket of Senpai

When boys put their hands in their pockets, it means they're hiding their feelings!" Chiharu has a boyfriend that is very, VERY quiet. At first, she didn't mind at all that he rarely spoke because she believed that she was fine as long as their feelings could be conveyed. Soon, though, she comes to realize certain things that makes her feel extremely anxious towards him... Why does he always keep his hands in his pocket?