The titular antagonist of the series. Tomie is a young woman and horror monster whose nature is left intentionally unexplained in full. Men (and in rare instances, other women) can't seem to stop themselves from chopping her into pieces, but Tomie is able to regenerate from anything into brand new Tomies. Some stories, particularly later ones, feature new Tomies distinct from the one featured in a previous story, but that Tomie is sure to act in exactly the same way as all the others.
- Adaptational Sexuality: While it's ambiguous whether Tomie is actually attracted to men (or just using them), she shows no interest in women in the manga; in the movie series, she is more clearly bisexual.
- The Ageless: Played with. A Tomie born from infecting a normal person with Tomie is able to grow older, with an infant Tomie being shown growing up to adulthood and old age. The moment she multiplies via regeneration, however she doesn't age anymore—and presumably the Tomies that split off from her don't age either.
- Alpha Bitch: She has that role when in a school setting, most notably "Photograph" and "Kiss".
- Ambiguous Situation: Is Tomie a monster, a girl with supernatural powers, an alien, or an embodiment of human lust and abuse? It's never explained why she can regenerate and hold such sway over others, and other characters can only guess at what happens and why based on what they observe of her.
- Facial Moles Symbolize Beauty: The vain Tomie, whom many men fall for, is characterized by a mole just under her eye.
- For the Evulz: Tomie often goes out of her way to ruin innocent lives for no reason. Special mention goes to Boy, where Tomie: molests an 8 year old boy, mocks his mother that the boy is hers now, drives the boy to murder, drives him to despair by saying she was only playing with him and then making the father of his family run off with her.
- From a Single Cell: Tomie is able to regenerate into a new Tomie, or several new Tomies, as long as some part of her remains. This even extends to infecting other people to turn into her with a handful of her cells, and one early story has her starting to form out of a rug with her fresh blood on it.
- Hive Mind: A strange case; all Tomies act with almost the exact same personality, and some Tomies are shown to share memories between each other as well, but they only sometimes act under a single intelligence and usually they're even competitive against other "rivals" Tomies. A few exceptions to this are shown in "Little Finger" or "The Basin of the Waterfall", where the Tomies there got along/acted as one while they were still regenerating.
- Jerkass: The woman is thoroughly unpleasant and loves ruining the lives of others for her own amusement.
- Kill It with Fire: Other Tomies will suggest killing their "rivals" by burning them, and it's eventually confirmed that the only thing that can kill a Tomie for good is to cremate her at the highest temperature possible. As "Little Finger" demonstrates, though, anything less than cremation won't be enough.
- Thanatos Gambit: In later stories, its clear Tomie intentionally endeavors to anger men and make them cut her into pieces, so as to create more Tomies.
- Troubling Unchildlike Behavior: Infants infected with Tomie in infancy grow up to be little girl versions of Tomie. Yasuko's Tomie sister, Ayaka, is shown as being bratty and trying to seduce older boys. By the time she's eight, she's also trying to get her rival little-girl-Tomies killed.
- Viral Transformation: Another way Tomie spreads herself; if some of her cells or blood is left in an unwitting victim (at least a female one), they end up transforming into another version of her.
- Was Once a Man: Possibly. Its ambiguous if the Tomie in he first story is the original one or simply got infected. Of course, people who were infected by Tomie clearly count.
- Would Hurt a Child: Tomie is shown sexually molesting an eight year old boy in one story.
Tomie's teacher in the very first story, who was carrying on an affair with her until she was brutally murdered. He shows up occasionally in some of the early stories, experimenting with Tomie's regeneration process under the pretense that she's his "daughter".
- Arc Villain: While Tomie herself shows up through the whole series, Takagi is this for the early half of the series. He intentionally mixes innocent people up in the horror that is Tomie and experiments with her regenerative process, ostensibly to learn how to stop it, until his last appearance in the Morita Hospital two-parter.
- Teacher/Student Romance: The way that his relationship with Tomie started in the first story. Although at first he didn't seem very happy about it after she came back from the dead, it's implied that her influence is what drove him to be obsessed with her after she was killed.
- Mad Scientist: He takes on this role in spirit after his first appearance, experimenting with Tomie using normal human girls as guinea pigs.
The protagonist of three Tomie stories in the first volume, and one of the few protagonists to survive her encounter with Tomie. A member of the photography club who secretly takes candid pictures of her male classmates for cash, Tsukiko's life becomes a nightmare when she takes a picture of the new rich girl in school, Tomie, and her photograph reveals her for what she really is.
- Camera Fiend: Tsukiko takes plenty of pictures, and this is what gets her in trouble. Apparently her skill as a photographer is one of the reasons that her picture of Tomie showed her as a monster. By the same token, she's able to take a picture of the old man's daughter that shows her as she was before she became a horrific Tomie experiment.
- Only Sane Man: She's one of the few protagonists to get mixed up in Tomie's affairs and live, mostly because she's able to keep her wits, not fall for any of Tomie's charm, and get the hell away whenever she has the chance.
- Screw This, I'm Out of Here!: How "Mansion" ends, with her escaping from the titular mansion after she finds out about the horror of Mr. Takagi's experiments. Not that she was that eager to enter in the first place.
The final protagonist of the Tomie series, present in the last three chapters. Yasuko is a poor, unattractive young woman who learns that her bratty little sister Ayaka is one of several children who were infected by Tomie in infancy. The man who reveals this, a disfigured male model named Ryo, explains that he did this as part of a revenge scheme against Tomie, to have her grow old and lose her beautiful looks. Yasuko is roped into his revenge scheme and charged with keeping Ayaka from getting harmed until old age. This is easier said than done.
- Deuteragonist: Yasuko is the main protagonist of the last arc. However, almost as much time is spent on Ryo and exploring his vendetta against Tomie.
- Patricide: Ends up having to kill her alcoholic father when he, too, falls for Ayaka.
- Revenge: Her motive for keeping Ayaka safe is at first because she's her sister, and because Ryo tells her to. After she accepts how horrible Ayaka really is, though, Yasuko tries to help her grow old and lose her looks as revenge for being an Ungrateful Bastard.
- The Unfavorite: As a result of her little sister being a Tomie, Yasuko is viewed as plain by comparison, at least by their father...
A male model who was once obsessed with his good looks, he ran afoul of a Tomie when he insisted that he was prettier than her. After being scarred by one of her goons, he tried to take revenge on her but ended up severely burned, permanently disfiguring him. Mocked and treated poorly by subsequent Tomies, Ryo hatched a plan to take Tomie's good looks away by infecting infants with Tomie and watching at least one of them grow to old age.
- Mr. Exposition: He explains even more about how Tomies work than Mr. Takagi, evidently learning a lot about them in his travels.
- The Narcissist: Ryo was obsessed with his looks. Even Tomie's face was nothing to his, in his eyes. As a result the ugliness of his burns was too much for him to take.
- Revenge: His entire motivation; his looks were everything to him and Tomie took them away, so he wants to see the proud and vain Tomie reduced to an old crone.
- Would Hurt a Child: He intentionally infected baby girls with Tomie.