The most beloved fish in the world by children, Rainbow Fish, has lost his sparkling scale! When he goes to look into the deep sea, he loses his glittering scale, the only one left. He dives into the sea, overcoming everyone's attempts to stop him.
(Source: Deepl with edits)
Narrative fiction, heartwarming story
The book is fully written in hiragana with spaces between the words.
You can read it for free by watching a read aloud on YouTube: https://youtu.be/pmCdVcOKbu4?si=eJoV_vaNJP7hJz7U
This is a sequel to the famous Rainbow Fish book by the same author. The rainbow fish (虹魚 にじうお) loses his last shiny scale and goes on an adventure to find it.
At their current ratings, this book is listed on learn natively as harder than the original, but I actually think the original is a bit harder than this one