The Rainbow Fish series for ages 2 and up! This is the second volume of the popular "Rainbow Fish" series for younger children, with a smaller version and easy-to-read text. When the fish leave Striped Fish out of the group, Rainbow Fish and his friends are in danger!
(Source: Deepl with edits)
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/rE2rjm0h8uc?si=fhFP9XQWD10me3GN
This is a sequel to the famous Rainbow Fish (虹魚 にじうお) book by the same author. There are two editions of this book. This one is shorter with simplified text.