This episode is the first introduction of Ryuunosuke and her father to the regular cast.
Ataru, Lum, Shinobu and Mendou go to the beach, but find that the day is so cold that none of the shops are open, except for one little teashop where two people, Ryuunosuke and her father are working.
Ryuunosuke and her father are both at odds with each other regarding the running of the teashop, and are constantly fighting with each other. The group decide to help Ryuunosuke and her father settle their differences, especially after Ryuunosuke reveals that she is actually a girl, raised as a boy.
Later, Ryuunosuke and her father arrive at Tomobiki High School, to enroll her as a student. Ryuunosuke wants to wear the girls' school uniform, but her father is unsympathetic to her wishes, causing Ataru and his friends to try to take matters into their own hands.