Tobimaro Mizunokoji is the heir to the Mizunokoji sporting goods empire. Shuutaro Mendo's baseball playing, starry-eyed, childhood rival.
For generations the two wealthiest families in Japan, the Mizunokoji clan descended from Japanese nobles and the Mendo clan descended from the samurai, have been feuding. As their families fought so did Shuutaro and Tobimaro. A battle for superiority that has continued from childhood to the present day. They even still address each other as "Shuu-chan" and "Ton-chan" as they did when they were children.
Their rivalry has brought forth many duels between the two proud heirs. Their most sacred duel happens to be in the form of an annual baseball match with their honour on the line. But every game they've played so far has ended in a tie (actually a double knock out). To prepare for the game Tobimaro lives in the mountains, rigorously training for the their annual duel even though the training involved more martial arts than actual baseball. In the mountains Tobimaro had nothing to eat so he had to live on baseballs to survive. Because of this tendency to inhale balls he often swallows the baseball in the middle of a game.
Ton-chan has a certain mistrust and dislike of women which stems from his childhood with his rival's sadistic sister Ryoko. Stangely even though he doesn't like women, his personal secret police and servants are women. He is also comes to care deeply and become protective of his sister Asuka, whom he had recently met for the frist time.
Tobimaro is what you'd call an eccentric, if not only old fashioned. He rarely bathes, wears a torn and ragged samurai robe and often prefers to live life as it once was in ancient Japan. His looks and habits conceal the actual wealth that he possess.
Tobimaro has dedicated his entire existence to baseball and takes a warriors approach to the sport. But he's also a wimp and a screw-up which gives him a combination of stoic nobility and goofiness. He is an honourable fellow. True honour, not the affectation that Mendo puts on. Obsessed with defeating his eternal rival he constantly initiates competitions often involving strange twists on everyday sports.
To clairify one last thing, when I said he was starry-eyed, that wasn't a metaphor. His pupils really do have stars in them. Takahashi made him this way as a parody of 70's melodramatic sports manga where the hero had big starry eyes burning with passion and optomism. It's later turned into a running character joke since his whole family have the same distinguishing feature.
Notes about the name
Tobimaro's family name of Mizunokoji is a play on the real-life Mizuno sporting goods company which is known best for their baseball equipment.
Voice: Shimada Bin
Tobimaro's voice actor has also done the voice of Nakajima from You're Under Arrest! and Sentaroh from Ranma ½.