Kashima Ryuuichi: He is a high school student. After the death of his parents, he and his younger brother are adopted by the chairwoman. He cares for his brother and works at the school's daycare outside of lesson hours. He is considered likeable by the daycare children and practically everyone he meets.

Hayato Kamitani: He is Ryuu's stoic classmate and fellow member of the Babysitting Club. The older brother of Taka, who calls him aniki {formal for "older brother"}.

Maria Inomata: She is a serious student ranked 1st in the advanced class (1-A). She is a stickler for the rules and scolds students who go to school for purposes other than to study. Over the course of the series, she makes friends and becomes less strict towards herself and those around her.

Ushimaru Yuki: She is Ryuuichi's classmate with a secret crush on him. A member of the tennis club. She is unused to being around children and gets overwhelmed by them teasing her. She becomes friends with Inomata (in part due to their mutual like for Ryuuichi).

Usaida Yoshihito: He is the sleepy daycare worker and only official employee at the Morinomiya daycare. Secretly an earnest and hard-working person.

Taka Kamitani: He is Hayato's bratty little baby brother and one of the children at the daycare. The son of science teacher Shizuka Kamitani and chemistry teacher Taizo Hebihara. Despite his confident nature, he actually cries easily. He is Kotarou's self-proclaimed best friend.

Kotaro Kashima: He is Ryuuichi's younger baby brother. He's very attached to his older brother, as their parents' many trips left Ryuuichi to care for him. He isn't very talkative, but his facial expressions can give away what he's feeling. He is very good friends with everyone in daycare.

Kirin Kumatsuka: She is The oldest baby girl in the daycare, Kirin is the daughter of the drama teacher, Yayoi Kumatsuka, and a freelance photographer, Satoru Kumatsuka. She's very sweet and friendly, but has a stubborn side that can cause her to argue with Hayato.

Takuma Mamizuka: He is the older, energetic baby Mamizuka twin. A son of PE teacher Umi Mamizuka and actor Kousuke Mamizuka. He is cared for at the Babysitting Club.

Kazuma Mamizuka: He is the younger, teary baby Mamizuka. twin. A son of PE teacher Umi Mamizuka and actor Kousuke Mamizuka. He is cared for at the Babysitting Club.

Sawatari Midori: She is the only baby in the daycare and normally under Usaida's responsibility. The daughter of Yukari Sawatori, who works in the high school office, and Yutaka Sawatori, an archeologist.

Shizuka Kamitani: She is Taka and Hayato's mother. The middle school science teacher and formerly married to Taizo Hebihara.

Saikawa Keigo: He is an employee of the chairwoman whom very little is known about. He is considered her butler, though his official job title is unknown, but also works as her secretary. He is quick to adapt to any situation {even if totally unprepared for it}. He can be overly sincere, responding excessively to feedback.

Sawatari Yukari: She is the kind mother of baby Midori and married to Yutaka. Works in the high school office as a receptionist.

Taizo Hebihara: He is the infamously strict high school chemistry teacher and Taka and Hayato's father. Divorced from Shizuka

Morinomiya Youko: She is the school's stern but secretly caring chairwoman. Her son and daughter-in-law died on the same plane crash as the Kashima brothers' parents. Ryuuichi and Kotarou call her obaa-san or baa-san {"grandmother"} though she becomes angry whenever Kotarou calls her "fluffy" in reference to her hair.

Mamizuka Kousuke: He is married to Umi and father of the twins Takuma and Kazuma. A popular actor who is easily upset and frequently tears up. He is often put in a bad position when his performances have significant effects on his children's behaviour.

Kumatsuka Satoru: He is Kirin's doting dad and a photographer. He is possessive of his daughter and paranoid that any boys near Kirin will take her from him. His dislike of men and boys being near his daughter