The story follows the sometimes happy, sometimes sad, and a tad stressful daily life of "some sort of small, cute creature" (Nanka Chiisakute Kawaii Yatsu) known as Chiikawa. Chiikawa enjoys delicious food with bees and rabbits, toils hard every day for the rewards of work, and still maintains a smile.

Ten’ikai General Hospital’s Supervisory Department of Diagnostic Pathology handles cases other physicians deem too difficult to treat. It’s also where bizarre mysteries surface, from unexplained illnesses to strange murders even the police can’t solve. At the center of it all is Takao Ameku, a brilliant doctor determined to reveal the shocking truth behind these anomalies.

Chiikawa and friends set off on a whimsical summer adventure to a mysterious island said to hide a long-lost mermaid secret. What starts as a fun getaway quickly turns into a heartwarming journey filled with surprises, gentle thrills, and adorable chaos. With sparkling seas, strange legends, and unforgettable encounters, the trio learns about courage, friendship, and the magic hidden in small moments.