Yunika harbors a deep resentment toward her best friend Risa's boyfriend, Kazuma, yet finds herself secretly aroused by their intimacy. After a chance encounter during a rainstorm leads to a clandestine sexual encounter between Yunika and Kazuma, the tension grows during a group trip to a hot spring. As Risa and Kazuma indulge in their passion in secret, Yunika battles her conflicting emotions of jealousy and forbidden desire.