Нішіда Кай

Kai is Risaki's younger brother and the last member of the Drama Research Society. He was drafted against his will by his sister at the same time Mugi joined. Thus, the two of them share an odd friendship since both do not really want to be members of the club. Later on, he gradually develops romantic feelings towards her. Kai often gets forced by his sister to do things for the club at the expense of himself. (Source: Wikipedia)