[3] Tohru, age 16, is an orphaned high school student who, after meeting Yuki, Kyo, and Shigure Sohma, learns that thirteen members of the Sohma family are possessed by the animals of the Chinese zodiac and turn into their animal forms if they are embraced by anyone of the opposite sex or when their bodies come under a great deal of stress or are greatly weakened.

[4] As the series progresses, Tohru meets the rest of the zodiac and the family's mysterious head, Akito Sohma, and resolves to break the curse that burdens them.

[7] When asked how she came up with Tohru's personality and background, she said: I thought that for a girl to accept other people's feelings so wholeheartedly, she'd have to have a slightly unusual way of looking at things so that she wouldn't be crushed by having so much empathy.

At the start of the series, she is living in a tent rather than staying with her friends, Arisa Uotani and Saki Hanajima, to avoid being a burden to them,[4] and she has an after-school job as an office janitor to pay her tuition fees so that her grandfather does not have to.

[19] Tohru is distressed whenever she feels she is being "unfaithful" to her mother, for example, when she gets failing marks on end-of-term exams, thus endangering her promise to graduate high school,[20] or when she falls in love with Kyo.

[21][22] Tohru eventually realizes that her vow is an attempt to cling to the past, and that Kyoko would have wanted her to move on and fall in love with someone else.

[23] A few months before the series begins, Tohru's mother died in a car accident, leaving her an orphan in the care of her grandfather.

When her tent is buried in a landslide during a rainstorm, Shigure convinces her to move in with him and Yuki as housekeeper in exchange for room and board.

Tohru promises to keep their secret, under the threat of having her memories of them erased—a compromise agreed to by Akito Sohma, the mysterious head of the family, who orders Kyo to live with Shigure as well.

[28] Kyo initially appears to dislike Tohru, but he, like Yuki, is "drawn" to her kind heart and gentle demeanor.

Gradually Tohru meets the other cursed members of the Sohma family, and through her kindness and sympathy is able to help Hatori,[29] Ayame,[30] Kisa,[31] Hiro,[32] and Ritsu.

[33] Her encouragement to Kisa also helps Yuki face his own self-doubts and accept becoming president of the student council;[31] in addition he knows, by a cap Tohru treasures,[14] that she is the lost little girl he once led home, an act that showed him that he was not as unneeded by others as Akito claimed.

[41] When she learns that the feared Akito is the "god" of the zodiac and of the bet he made with Kyo, which could result in the cat being confined for life, she resolves to break the curse.

As she angrily confronts her, however, Tohru realizes that she is trapped by the past as much as she herself has been, by clinging to her mother's memory, and she extends her hand in friendship to Akito and introduces herself as a new start.

[51] In the last chapter, she and Kyo are shown packing to move to another city to continue his martial arts training, so that eventually he can inherit Kazuma's dojo, and in the final pages, it is revealed that they got married and had a son and a granddaughter.