Natsuki Suzuura is a teenage girl with green eyes and neck-length brown hair, typically dressed in her school uniform and sneakers. She lives next door to Kenji Seki, sharing a close yet contentious childhood friendship marked by frequent arguments and physical altercations like hitting him when annoyed, stemming from underlying affection; they once used the nicknames "Ken-chan" and "Natsu." Athletic and energetic, she participates in track and field and often incorporates gymnastic movements into her daily behavior.

Her relationship with Kenji involves complex, unspoken emotions. Natsuki harbors longstanding romantic feelings but masks them with teasing or denial, causing significant emotional conflict, especially when Kenji shows interest in Kahori Harukawa. A pivotal childhood sacrifice defines her loyalty: when Kenji faced a life-threatening coma, she traded her latent psychic abilities to ensure his recovery, leaving her powerless, an act he remains unaware of for most of their interactions.

Her development centers on navigating jealousy and insecurity as Kahori and the psychic transfer student Ryoichi Kyogoku become central to Kenji's life. She experiences intense turmoil during psychic manipulations targeting the school, culminating in a tearful confrontation with Kahori about Kenji's feelings. Following a climactic event involving time travel and memory alteration, she temporarily forgets Kenji's existence. After he returns to the present timeline, her memories are restored, and she reverts to their familiar dynamic, calling him "baka" in their final interaction, reaffirming her tsundere nature.

Her friendships include a rapport with Kahori, whom she questions about romantic interests, though she downplays her connection to Kenji as merely neighbors when asked. Throughout the narrative, her actions consistently reflect a protective stance toward Kenji, even amid their quarrels.