Kobato Haneda, raised as the younger sister of Takashi Haneda but actually the cousin of Yōji Haneda, lives with Takashi. She shoulders significant household responsibilities, including daily breakfast preparation. Despite her caring nature, Kobato maintains emotional distance from Takashi, confusing him, though she holds him in high regard and expresses deep affection for him to others like her friend Akira. Her reserved personality makes social connections challenging, resulting in few but deeply valued friendships. She exhibits a gentle, warm, and selfless demeanor, prioritizing others' well-being and rarely showing anger.

Kobato possesses detailed knowledge of Takashi's dissociative identity disorder, instantly differentiating between the distinct personalities of Takashi, Shūsuke Chitose, Hayato Narita, and Karura Itami. She understands their individual habits and preferences, such as favorite foods. Kobato attributes Yōji's retreat into his subconscious and the emergence of the alternate personalities partly to herself. This fuels her devoted, sacrificial care for Takashi, Shūsuke, and Hayato—with whom she maintains positive relationships—in hopes of Yōji's return.