Sister Complex!!

When Ichitaro's mother's new spouse brings in a girl from previous marriage Kurumi, he was looking forward for life with pretty little sister under one roof. However she gives him an ice cold shower on their first meeting. Ichitaro has nothing to do, but accept the reality, especially since he was recently confessed to by a classmate and was ready to enter his period of popularity among girls. However, it turns out Kurumi has sudden spikes of primal instinct and Ichitaro is her target.