Sakiko is a young girl who's in the same class as the Marui sisters in the Mitsudomoe franchise.
She is obsessed with the occult and has convinced herself that Hitoha Marui is an exorcist and that the elementary school is a hotbed for supernatural activity. This has lead to many bizarre situations and events involving late night school visits and things done to people sleeping in the nurse's office.
Sakiko is a character in both Mitsudomoe anime series, Mitsudomoe and Mitsudomoe Zoryochu!, published by Aniplex with animation production by Bridge and the manga series Mitsudomoe, published by Akita Shoten and serialized in Weekly Shonen Champion. Sakiko's original design is credited to manga writer and illustrator Norio Sakurai while her anime version is credited to Takaharu Okuma. Sakiko makes her first voiced anime appearance in Mitsudome episode 3, "So Many Sinners".