One day, Itsuki loses her house key and urinates at the entrance. - So, she asks her neighbor Imaoka to use the toilet, but... she can't make it in time and ends up leaking at the entrance. - When Itsuki apologizes, Imaoka, who has been lusting after her voluptuous body for some time, plays with her, using the secret of her incontinence... - Imaoka shows interest in Itsuki, who shows a sensitive reaction to her butthole, and fucks her anus mercilessly. - The stimulation that cannot be felt in the vagina is deeply engraved in her mind. - Then, Itsuki visits Imaoka's house again...