In the second season of Amanchu!, Hikari Kohinata and Futaba Ooki continue to explore the wonders of scuba diving and everyday life together. Despite their contrasting backgrounds, Hikari from a seaside town and Futaba from Tokyo, the two girls form a strong bond at Yumegaoka High School. Futaba, usually reserved, finds a kindred spirit in the cheerful Hikari, who inspires her to embrace new experiences and find happiness in the little things. Encouraged by their friendship, Futaba overcomes her fears, passes the Open Water Diver exam, and now aims to achieve the Advanced Open Water Diver certification.