Hitomi's peaceful married life with her husband, Hiroki, is thrown into turmoil when his older brother, Soji, suddenly appears and moves in as a temporary resident. After a month of living under the same roof, Soji unexpectedly brings up nostalgic memories of catching insects together during their childhood. While Hiroki was satisfied merely catching them, Soji always enjoyed caring for the creatures afterward—just like how his approach to women is more attentive and intense. Soon after, Soji makes a sudden, aggressive advance on Hitomi. She desperately tries to resist, but her mature, sensual body gradually succumbs to his rough, passionate touch. As forbidden desire seeps through the cracks of everyday life, Hitomi's relationship with her husband takes a drastic, irreversible turn.