Kyōko Takimoto is a high school student and Sakura Yamauchi's best friend. She possesses a slim build and short brown hair initially reaching the bottom of her neck, featuring uneven bangs swept upward that cover part of her forehead and thick locks framing her face. Her eyes are thin with reddish-brown pupils, and she has a small mole under her left eye. After Sakura's death, her hair grows longer, extending just below her chin.

Kyōko exhibits a cold, aggressive, and stubborn demeanor, especially toward those she distrusts. Her protectiveness over Sakura manifests as hostility toward Haruki Shiga, whom she finds suspicious. She repeatedly tries to dissuade Sakura from associating with him, though Sakura consistently rejects these efforts. Despite her outward abrasiveness, Kyōko deeply cares for those close to her, a warmth that surfaces openly only after Sakura's death.

Kyōko first interrupts a meal between Sakura and Haruki, mistakenly assuming they are on a date and criticizing Sakura's choice of company. She later confronts Haruki on a school balcony, demanding an explanation for his trip with Sakura. When he refuses to answer, she knocks his book over the railing and threatens him, warning she will kill him if anything happens to Sakura. During a hospital visit, she witnesses Sakura and Haruki embracing, sparking fury; Sakura intercepts her to allow Haruki to escape. Kyōko attends Sakura's funeral, visibly mourning alongside other friends.

After the funeral, Haruki invites Kyōko to a café and gives her Sakura's diary, "Living with Dying," detailing Sakura's illness and final thoughts. Reading it reduces Kyōko to tears, forcing her to confront Sakura's hidden struggles. Haruki then asks Kyōko to be his friend. One year later, Kyōko and Haruki visit Sakura's grave together, demonstrating their reconciled friendship. During this visit, Kyōko offers gum to Haruki. They proceed to visit Sakura's family afterward.

Kyōko's relationship with Sakura is central, defined by mutual devotion and protectiveness. Her bond with Haruki evolves from antagonism to friendship, cemented through shared grief and Sakura's diary. Her dynamic with Issei Miyata begins combatively, as she often scolds or physically chastises him for laziness. However, a post-credits scene implies romantic development between them. A sequel novel confirms their marriage and the birth of their daughter, Anzu.

Kyōko's name incorporates kanji meaning "waterfall" (滝), "origin" (本), "respect" (恭), and "child" (子).