Kyoko Fukada as Chiyomi Horikiri: Another top student and calligrapher who is Susumu's girlfriend. She shrinks down to 16 cm(6 inches) from a curse when he leaves her.
Kazunari Ninomiya as Susumu Minami: A handsome runner who is Chiyomi's boyfriend and the object of Reika's affections.
Mao Miyaji as Reika Nomura: A top class student who uses her looks to try and win Minami over. However, Susumu doesn't like her for a personal reason. Wasn't very nice to Chiyomi until much later when Reika realizes how much she did relate to her.
Asami Abe as Sakura Minami: Susumu's younger sister.
Masahiko Nishimura as Kenichi Minami: Susumu's father who is hard on him to focus on his studies. He came close a few times to discovering Chiyomi in his son's room.
Seiichi Tanabe as Seiichiro Kusakabe: Chiyomi's 2nd cousin and Senji's nephew who works as a teacher.
Soichiro Kitamura as Senji Horikiri: Chiyomi's grandfather who taught her calligraphy and was strict in raising her when her mother(Senji's daughter), Mariko died. When he suffered another heart attack, Susumu and Chiyomi does the right thing to explain themselves to him.
Tomoya Ishii as Koshiku Ohara: Susumu's best friend who finds out about Chiyomi in her shrunken form. Ohara is the only one who helped find ways to keep others from finding the truth.
Yuko Natori as Takeko Minami: Susumu's mother who helps Reika cope with her lack of communication with her own parents.
Maika Yamamoto as Chiyomi Horikiri: Member of the dance club and writing her own fantasy stories. Former childhood friends and sweetheart of Shunichi. She shrinks to 15 cm after wishing to go back to her childhood days and a fight she had with her parents
Taishi Nakagawa as Shunichi Minami: Former childhood friend and sweetheart of Chiyomi who formerly practiced Kendo. He is studying to be a doctor
Erina Nakayama as Sayuri Nomura: A classmate of both Shunichi and Chiyomi. She relates to Shunichi due to a similar situation she is in with her mother disappearing. Most of the students dislikes Sayuri and gives her the nickname "Pheromones", due to her being overly sexual. When she tries to admit her feelings for Shunichi, he turns her down and admits his own feelings for Chiyomi.
Mirai Suzuki as Riku Tagaki: Another classmate who is friends with Chiyomi and Ami. Riku has feelings for Chiyomi and doesn't like Shunichi for the way he treats her. He suspects that Minami had something to do with Chiyomi's disappearance. In episode 9, Riku learns the truth and confronted Shunichi about it. This leads to him learning about Chiyomi's shrunken form and her true reason in hiding away.
Riko Yoshida as Asuka Horikiri: Chiyomi's sister who is kind to her. Friends with Shunichi Minami and is the only one aside Sayuri he hasn't acted cold around. In Episode 8: she is the first one who learns about Chiyomi's shrunken form and tries to keep the secret.
Naomi Akimoto as Noriko Horikiri: Chiyomi's strict mother who is a realist, but is also a secret romantic. She finds Chiyomi in her shrunken form in Episode 10 after Shunichi is in an accident.
Narimi Arimori as Emiko Minami: Shunichi's mother who is worried about her husband and son. She later discovers his relationship with Kana and files for divorce.
Moe Sasaki as Ami Mikimoto: Chiyomi's best friend in the same dance club. She has a crush on Riku.
Ichirota Miyagawa as Noburo Minami: Shunichi's father who mysteriously disappears during junior high. He taught Shunichi, Kendo. It is eventually revealed in episode 5 that Noburo is in a relationship with Sayuri's mother, Kana.
Kouichi Ohori as Jouji Horikiri: Chiyomi's father who works as a florist. He is also strict with Chiyomi when it comes to her future. In Episode 10, he learns about Chiyomi being tiny and fainted on the sight of seeing her in Noriko's purse
Kazue Tsunogae as Tomiko Minami: Shunichi's grandmother who tells him and Chiyomi the legends of Issun-boshi and the one-inch princess known as Issun-hime. Tomiko learns about Chiyomi's shrinking in episode 6.