Her husband left home after taking a mistress, leaving Sanae as the sole provider for the family. One day, her son brings home an older girlfriend and announces their engagement. Sanae is overwhelmed with shock and confusion, left speechless by the news. That night, as her son prepares to leave with his girlfriend, she stops him at the door, overcome by loneliness, and begins masturbating. Just then, she receives a message from her son inviting her to a family party. When his friend arrives, an unexpected encounter unfolds, stirring emotions deep within her.