Tomo is a very hyper energetic and competitive girl, despite being nonathletic and a slacker. She is extremely impulsive and never considers—nor cares about—the consequences of anything she says or does. She and Yomi are seen as manzai comedians with Tomo acting as the boke and Yomi acting as the tsukkomi. This usually irritates those around her, especially Yomi, her classmate since elementary school. Because of this, and her usually awful test scores (in which she has a perverse pride), she is the de facto leader of the "Bonkuras" (translated as "Knuckleheads" or "Bonklers" in the anime and "Numbnuts" in the manga), along with Osaka and Kagura. She is, however, capable of doing well if she tries—though the only notable instance of this is getting admitted to their prestigious high school, and she only did this to annoy Yomi. She also likes to irritate Yomi by teasing her about her weight insecurity, such as when Yomi wrote into a radio show under the name "Tearful Little Diet Girl." Tomo's favorite food is bananas.
In fact, she spends much of her energy on annoying others. During the second trip to Chiyo's summer home, Tomo grabbed Chiyo's house keys and flung them into the overgrown yard to see what would happen if they lost them. She constantly makes fun of the rest of the girls, particularly Chiyo for being a kid. However, Tomo cares for her friends in her own way, as shown in near the series conclusion when she starts what becomes a standing ovation for Chiyo when she's is honored as the top of the class. She also attempted to cheer Kagura up after unintentionally making her feel guilty when they were preparing for the third year Sports Festival. Tomo is also a delusional egomaniac who constantly imagines that she is competing with others, even when no comparison can be made. For example, she frequently challenges the athletic Sakaki in races (which Sakaki easily wins), and expects to be named valedictorian despite her consistently poor grades. In the manga, when Chiyo announces that she is turning 12 years old, Tomo proclaims she is already 17, as if that were an accomplishment. She is a fan of the manga and anime series Lupin III and sometimes compares herself to the sexy Fujiko Mine, despite being completely different in appearance and personality.
Tomo gave Ayumu Kasuga the nickname "Osaka" because she came from Osaka. In the manga, she creates other obvious names: she once had a hamster named Hamu and now owns a dog named Kuro, meaning "black" (in translation, this was changed to a cat named Whiskers and a dog named Spot). Tomo frequently refers to manzai comedians, and expects Osaka to join in (manzai being a form of stand-up comedy particularly associated with the Osaka region).
Tomo is more interested in dirty stories and sexuality in general than the rest of the cast, and asks the adults for "information" during the summer retreats (once getting sordid results from a drunken Minamo). Dirty jokes are Tomo's forte, including a particularly nasty one in the manga only, when Yukari and Minamo appeared in their old school uniforms during the third year Sports Festival, threatening to arrest them on prostitution charges. Despite her interest, Tomo remains as boyfriend-less as the rest of the girls.
Tomo is the assistant class representative despite her poor grades, because no one else volunteered. When the girls enter senior year, Tomo announces plans to become a policewoman, even one day entering Interpol (like Lupin's nemesis, Inspector Zenigata in Lupin III) despite having no idea how to get started as an Interpol agent. She does, however, successfully pass a university entrance exam—before Yomi did, much to the latter's dismay.
Tomo's surname means 'waterfall field.' and her given name means 'wisdom'. She's 154 cm (5ft 0.6in) tall.