In canonTomo and Yomi have been in the same class since grade school and stay together despite the obvious differences in their values and personalities – Yomi is ambitious and mature, or so she likes to come across, while Tomo is a slacker who doesn't give a care for school work and loves to annoy others.
Because Yomi has a short temper and always gets angry at Tomo when she teases her, Tomo only keeps doing so. A notable occurence of this was when the two of them were graduating from middle school and Yomi tried to get into a prestigious high school. Tomo told her she would go there too, and when Yomi believed this to be impossible, Tomo studied harder than ever only to have something to rub in Yomi's face. Despite everything, Tomo seems to know Yomi better than anyone. She immediately noticed not only that Yomi had gained weight, but also understood that she was going on a diet and saw this as an opportunity to make Yomi uncomfortable by bringing up. She also appeared to know from before that Yomi was terrible at singing, even though she was good at other things such as studying and sports. In some ways they are similar in their reactions and opinions of people, such as Kimura-sensei. Once, Tomo pointed out that Yomi had a nice body, as well as book smarts, in an irritated manner.
During their second year of high school, Yomi said that she hoped she would end up in a different class from that of Tomo's, because she was fed up with the two of them always being together. She also hoped that they would be in a different group when the class travelled to Okinawa, even though this was unlikely because the class would be divided into groups of six (Yomi's and Tomo's best friends being Osaka, Kagura, Sakaki and Chiyo, six in total) and only one group would consist of five people. However, when it was time to go to college, Yomi applied to a different college than Tomo did. Though Tomo got in before Yomi which annoyed her tremendously, not least Tomo's efforts to "console" her and implying that Yomi might not get in at all, even though they both knew Yomi was a much better student. Nontheless, Yomi got accepted and because of Tomo saying Yomi was too heavy to toss up into the air in celebration, they did this to Chiyo-chan instead.
Because Yomi and Tomo fight and argue often, most people in the series' fandom think they are a coupling, which has gained quite a large following. There is a lot of artwork, fanfics and AMVs related to the pairing to be found online.