After losing her mother at a young age, Nanami Simpson moves in with her marine biologist father, Scott Simpson, aboard the research vessel Peperonchino. Together, they embark on a quest to find the mythical Glowing Whale. When they stumble upon the remains of one, Scott shifts his focus to protecting these majestic creatures. Nanami forms a deep bond with an Orca named Tico, swimming with it daily. To her father's amazement, she discovers the ability to breathe underwater. A dangerous incident leads to a miraculous rescue by a Glowing Whale, impressing Scott as he witnesses its magnificence for the first time.