At the center of the plot is Tomoya Mizuhara, a young boy of 13 who acquires a new older sister upon his father's remarriage. Ichika, 17 and somewhat peculiar, displays an intense and sometimes unnerving fondness for Tomoya. Adding to the complexity of the situation, Ichika's close companion Ruri embodies the quintessential sadistic personality. Additionally, Ichika's friend Marina - who is of mixed Japanese and Caucasian heritage - boasts an impressive bosom.