The best way to get a free EPUB version legally is through your local public library. Most libraries partner with digital distribution platforms to lend e-books directly to your device:
Follow (the publisher) and Genki Kawamura on social media. Occasionally, they offer free EPUB downloads for World Cat Day (February 22 in Japan) or during mental health awareness months. Sign up for their newsletters. if cats disappeared from the world epub free
If you want to read the book immediately, digital subscription platforms offer free trial periods that allow you to read the book at no cost: The best way to get a free EPUB