Mugen is rude, vulgar, and often thinks highly of himself. Much of his past is a mystery. He was born on the Ryukyu Islands, never knew his parents, and was a former pirate. After an incident forced him to fake his death, he became a vagabond. But things changed after he met Jin and Fuu. Though very rough around the edges, he has a mutual understanding with Jin and cares for Fuu more than he lets out, considering he usually ends up going after her whenever she gets kidnapped. His fighting style is described as a "champloo," which means "mix." It combines all sorts of martial arts, unorthodox swordplay and break dancing. He relies on instinct and reflex to surprise his enemies. His style of clothing represents the future, whereas Jin's represents the past. His black hair is usually untidy, and is similar in shape to an afro.

Second year in Kasensou Private Preparatory Academy. Childhood friend of Rintarou's, and slow by nature. Speaks in a very wavy manner, and seems to always be smiling and having fun. She's quite the optimist. She has trouble understanding complicated theories, but doesn't mind as long as it's enjoyable. Doesn't like people arguing, and is depressed when things are unpleasant. Though she'd like to ease the situation in such cases, she's not really good at reading between the lines. She often went with her grandmother to see the stars on her grandmother's back. Because of that, she has a habit of reaching her arm out to the sky at times, which has led Rintarou to naming it the "Stardust Shakehand." She abruptly does this (even if she's talking with someone), which surprises everyone around her.