In a Japanese SEO spam hack, a hacker creates new pages with autogenerated Japanese text on your website. They use these pages for monetary benefits like providing sponsored backlinks or affiliate links to other websites. The process is as follows:

1. Firstly, the hacker gets property owner authentication in your Google search console.
2. Then the hacker manipulates crucial settings like Sitemaps or Geotargeting (International targeting and multilingual versions of your site).
3. At last, the hacker spams the website by creating new pages with Japanese text.
4. On clicking the spam URLs, you will be redirected to a phishing/ads pages or it will return a 404 error.