Koutarou Nanbara 南原耕太郎

He is the self-proclaimed "best friend and worst enemy" of Kazuya Saotome.

Nanbara is very rich with an eccentric, egomaniacal personality. He is jealous of constantly being outdone in projects by the poor Kazuya and will do anything to see him suffer. It was his virus that caused Kazuya to inadvertently to order May. Nanbara gets Sara do his chores by offering ramen in exchange. Though very antagonistic against May in her smaller form, he falls head over heels in love when she is enlarged to human size.

It was later revealed that he and Kazuya will form the Cyberdyne Corporation that produces the Cyberdolls and will be run by their descendants.