Mamoru is a very short 16 year old high school student, who just transferred to a new and prestigious school due to his high intellect. On his first day at school, he not only becomes a member of the student council, but also the boyfriend of fellow student council member, Ayako Takasu, who confessed her love for him earlier that day. He often comes off as a soft spoken character who is unsure of himself as to why Ayako would like him. He later learns that he too has the power to use Beatrice.