Tohma Seguchi (瀬口冬馬 Seguchi Tōma) is a fictional character from the hit anime and manga, Gravitation.
Keyboard player in Nittle Grasper and Mika Seguchi's husband. He is the head of N-G recording company and demands the best from all his contractual bands. Tohma is very protective of Eiri Yuki, and blames himself for the trauma Eiri suffered as a teenager, seing that he was the one who hired Yuki Kitazawa in the first place. He is unfailably polite to the point where he will refer to anybody (including his wife) as -san, and appears to be a friendly and even-tempered person (if also a ruthless businessman). As the series goes on, it becomes evident that much of this is a carefully construct mask: when Eiri is involved, Tohma has been known to be far from rational and soft-spoken.
Eiri Yuki Tohma's relationship with his brother-in-law is a mix of intense affection and guilt over his own failure to protect him from the disaster when they were living in New York. He is over-protective of Eiri to the point where it becomes an obsession, and there are several incidents that make it evident that between his business and Eiri, Eiri will always come first. The end of the anime suggests that Tohma's affection for Eiri also is romantic. This is more evident in the manga.
Shuichi Shindou Shuichi was a fan of Nittle Grasper (indeed, he claims that the reason he started with music at all was because of them), and idolized Tohma for his skills at the keyboard. Tohma was not initially interested in signing Bad Luck to N-G Records; only after Sakano had taken them on did Tohma involve himself in helping them, and it is heavily suggested that the only reason he did so was because he approved of Shuichi's influence on Eiri. When their relationship appears to become a threat to Eiri's well-being, Tohma does not hesitate to use his position to threaten Shuichi into chosing between Eiri and the future of his band. Shuichi's greatest idol and Tohma's bandmate, Ryuichi Sakuma, thanks Tohma for not getting rid of Shuichi. Oddly enough, Tohma replies that he didn't because it was what Ryuichi wanted.
Mika Seguchi Tohma is married to Eiri's older sister, Mika. Their marriage took place three years prior to the beginning of the manga. While no one knows how long the engagement period was, it was Tohma that proposed. On the surface their relationship is formal, Tohma addressing his wife as, "Mika-san" in the series. One of their main interests is Eiri and his well-being. Tohma is not afraid to openly discuss his feelings for Eiri or react over-enthusiastically at the mere mention of his name in front of her. In return, Mika trusts Tohma with the well-being of her younger brother. In the manga, when Eiri falls ill (just as in the hospital in the anime,) Mika blames Tohma on the basis that N-G Studios should have kept the relationship between Shuichi and Eiri more quiet, thus less stress for Eiri. Her words make her husband cry, as he says that he only wants the best for Eiri, proving that Mika can hold her own in this marriage.
Later in the manga series Mika becomes pregnant, though news of being an expecting father doesn't halt Tohma's quest in interfering in Eiri's life. Eventually the stress becomes too much for Mika and she's put in the hospital in volume 10. It's probably then that Tohma realizes the amount of hurt he's heaping upon her and he (again) tearfully apologizes for everything. Mika, however, hugs him and tells him that he doesn't need to apologize, that Eiri can fit into their family.
The keyboardist of Grasper, the one in charge, called a "genius" because he wishes to be. After the breakup, he establishes his own label, as company President and devotes himself to his work as a producer. Since Grasper's revival, he has become an artist and producer. Regarding Eiri's past, which few people understand, he is the one that does.
- Tohma bears a striking physical resemblance to Quatre Raberba Winner of Gundam Wing. Ironically enough, both characters share the same Japanese seiyuu, Ai Orikasa.