Mamoru seems to be located in another school other than Seiyo Academy. He is mostly interested in exploring outer space. When he experienced the advantages of outer space, he always carries a book that focuses on facts of space.
Mamoru resembles of a boy with informally gray eyes and brown, short hair. His garments is a gray-colored uniform with a green neck tie; Mamoru can be always seen carrying a dark gray tote bag.
Confusion Character Change
When his Guardian Egg is extracted into a ? Egg, he doesn't seem to use some exact element, but stare at the sky, and declares to be in space.
He only appears in one episode as Mamoru Mizuno dream to be close to the space that was taken advantage of astronauts.