On a rainy day, Mato decides to follow Hikari as she boards a train, discovering that her only reason for doing so was to witness some blooming hydrangeas for a brief instant. Later, on a particularly hot day, Mato has the club play red light green light as punishment for skipping on their exam studies.

Futaba and Hikari follow the club's mascot, Cha, leading them to take a path that neither of them has been down before. Along the way, they come across a small kitten that appears to have been separated from her mother. With neither girl able to take the kitten in, they decide to ask around at school for a potential owner, eventually getting found by Mato, who reminds them of responsibility involved in taking care of a life. Hearing Futaba wants to help the kitten like she helped her, Hikari convinces her mother to let the kitten stay at her house until they can find an owner. Just then, the school's principal, who is Cha's owner, decides to take in the kitten, who is given the name Ohime.

While Futaba is away for a memorial at her country home, Hikari befriends a girl by the sea who is fascinated by a mother octopus guarding her young - Futaba is determined to befriend her. Meanwhile, Futaba works hard as a volunteer helping to set up the local fireworks festival, working hard enough to earn front row seats in the VIP section of the festival for her friends.

Futaba takes the underwater navigation tutorial but is brought crashing back to reality by the realization that she may be holding Hikari back - but is able to successfully complete it after she remembers all the lessons she had been taught by her friends. After watching the twins go on a night time dive, Futaba wrestles with the feeling that she may be holding Hikari back.

Futaba and Hikari spend an autumn day apart, and they both find autumn wonders of their own.

Futaba goes diving in a drysuit, as the gang looks to encounter the legendary Jet-Black Mermaid.

It's Halloween, and the Diving Club members find themselves in the midst of a special event in an amusement park. Hikari's in danger, and it's up to Futaba to be her knight in shining armor?

After meeting Peter in an encounter straight out of fantasy, Ai now gets transported to a fantasy world, where she meets someone she never expected to meet.

Ai can't accept how Peter parted with Mato-chan and her, and so she decides to head back to Neverland, only this time she has company.

Pikari ends up with a cold on her birthday, so Teko decides to visit her at home. She finds someone on the way, which leads to plans for another fun event once Pikari recovers.