Hina Tōmi is Hime Gotō's classmate and a member of the Meguro River Detective Agency. At school, she serves on the lunch committee. Her residence in a high-rise apartment building with concierge service indicates an affluent background. Her demeanor is somewhat showy and mature for her age. She initially displays a condescending attitude toward Hime, making insensitive remarks like asking if Hime is poor due to her single-parent household.

Her perception shifts dramatically after witnessing the elaborate ten-tiered Hina dolls at the Gotō home, revealing they are not financially disadvantaged. This realization challenges Hina's self-identity as the "rich girl," causing her pride to falter. Following this, she avoids discussing Kakushi Gotō’s profession and privately suspects he may be involved in illicit activities to afford such wealth.

Within the Meguro River Detective Agency, she participates in group discussions about unresolved cases and internal dynamics. In one instance, she questions the agency head's claim that one member is secretly an adult, pointing out that none of their cases have ever been conclusively solved. She also firmly believes Santa Claus does not exist.

The character derives from Nami Hitō in the author’s prior work, *Sayonara, Zetsubou-Sensei*.