Yu Aihara

Commander Sugata discovered the existence of the Royal Underground Empire Tube, a malignant force that desires to dominate the land, which is based underneath Japan. He recruits five young people, each one specializing in a style of martial arts, and teaches them in the ways of the mystical "Aura Power" energy. A year after he recruited and trained the Maskmen, Tube is ready to strike.

Shumpei sometimes sees his neighbor Keiko, but doesn't think much of her. One of Keiko's friends gives her the phone number of a single guy, but when she calls she recognizes him as Shumpei, and gives him the made up name 'Nana.' When they meet face to face, she pretends not to know him, but through their phone calls, they slowly start to fall in love.