With the upcoming five episodes/movie, they'll go beyond the manga so they're fine with adapting directly from the novels. These 17 episodes cover the first four novels and the eighth just came out, so there's already enough material for another season. There are even two collections of short stories if they need even more material.
FROM JAPAN, RRRRRRRRREIKOOOOOOOOOO HINOOOOOMOTOOOOOOOO
I’ll always dream about the alt reality where this franchise blew up. Fitting for a wrestling game, it’s got some fun characters/personalities and the way you unlocked heel personas was so cool.