"Ah, ah" - a common household scene [bathroom timing overlap]. "Mom, you go first," "Oh, I'm sorry." The son casually waits outside the door after yielding his turn to his mother. Suddenly, from inside the quiet hallway, a sound of urination leaks out - "Shaaa... Choro choro..." Hearing his mother's urination for the first time, the son feels a mix of embarrassment and an inexplicable urge to listen, his ears perked up in excitement. He realizes that a sexual feeling towards his mother has begun to sprout within him...