It depends. If you're reading manga on legitimate websites that have the rights to distribute it, it's not illegal. However, if you're getting it from illegal torrent sites or unlicensed platforms, then yes, it's against the law.
The legality of reading manga online depends on the source. Legitimate platforms with proper authorization make it legal. But most random sites offering free manga are likely illegal and can get you in trouble.
You can search for relevant subreddits dedicated to manga and look for posts or discussions about Monster manga. Some might have links or suggestions on where to read it.
There are several websites where you can read novels for free. Project Gutenberg offers a wide range of classic novels for free. Another option is ManyBooks, which has a large collection of free e - books. However, make sure to check the legality of the sources in your region.