Reiko is a single mother raising her son. Now a college student, her son is more interested in playing around than helping out at the family soba shop. Seeing how busy Reiko is, her son's friend, Shiro, offers to work part-time at the shop. While Shiro secretly sees his own mother's image in Reiko and wants to be helpful, he also harbors a twisted desire. After giving Reiko a Mother's Day gift at the end of his shift, Shiro can no longer suppress his overflowing lust...