Yuma Tonami is a character appearing throughout the To Heart 2 franchise and its spin-off To Heart 2: Dungeon Travelers. She has neck-length aqua-blue hair, green eyes, stands 158 cm tall, and has measurements of 85-57-81 cm. Her personality embodies the modern tsundere archetype, characterized by energetic, competitive, and short-tempered behavior, coupled with stubbornness and a tendency to become easily flustered. She frequently exhibits arrogance and rudeness, particularly towards Takaaki Kouno, whom she views as a rival.

Her interactions often begin with accidental bicycle collisions leading to challenges for duels or competitions against Takaaki. These encounters typically end in her defeat, followed by her habitual declaration, "Don't think you've already won this!" – a phrase that also names her unique skill in Dungeon Travelers, granting a 100% battle escape rate when her HP is low. Despite her confrontational attitude towards Takaaki, she harbors unacknowledged feelings for him.

Yuma shares a close friendship with Manaka Komaki and attends the same grade level as Takaaki, though in a neighboring class. Her activities include cycling, tennis, table tennis, and shopping. Her family background notes a grandfather connected to Kurusugawa Electronics, implying a potential future role for her within that business.

In Dungeon Travelers, she appears as downloadable content (DLC). Her initial equipment comprises a Kukri +2, Leather Shield +2, Leather Helmet +2, and Leather Armor +2. Her base stats at Level 1 are: HP: 46, TP: 16, ATK: 4, DEF: 3, INT: 4, RES: 3, DEX: 9, AGI: 7.

She features in OVAs like the Another Days series. Story elements include a memory alteration scenario where she participates in rewriting Takaaki’s memories, and a comedic segment where she pursues him alongside others to establish first-name familiarity. These portrayals reinforce her persistent rivalry and tsundere tendencies across the franchise's media.