Yui is married to a husband who works away from home, leaving her alone with her son. Though she knows it's wrong, she can't bear the loneliness and finds herself drawn into an intimate relationship with him. Even while waiting for her husband to return, their forbidden bond continues without pause. Yui stays vigilant, determined not to let her husband find out, yet she's constantly tormented by guilt and anxiety. Meanwhile, her son enjoys their secret affair, taking pleasure in how she turns to him during her husband's absence. Then one day, the moment her husband leaves, she finds herself attacked by her son... Caught between fear and confusion, Yui realizes she's already too far gone to turn back.