A school mystery about Rikka Mutsunori, a sixth grader who dreams of becoming a lawyer and confronts incidents at her new school. Often underestimated because of her small stature, Rikka relies on legal knowledge and determination to defend friends who have been accused, launching her own helping trial.

I do not want to stay silent when something feels wrong anymore.

Riko, a fifth grader, has inherited mysterious objects from her grandfather, who left on an expedition and never returned. When she discovers that a shrine's puddle leads to the sea, she joins Naito and her friend Ryoka on a dangerous adventure toward a legendary underwater city.

Beyond a puddle lies the sea, where Riko and her friends use strange tools and quick thinking to seek an underwater city.