Husband Junta lives with his wife, who is nearing her due date. With the birth of their first child approaching, his wife's older sister, Akari, comes to help with household chores. Gentle and mature, Akari is the complete opposite of her childish, self-centered sister, and Junta quickly finds himself smitten. After the baby is born healthy, they celebrate at home with a joyful party. But when Akari gets drunk and mistakes Junta for her own husband, an unexpected turn of events unfolds.