This series is a tier above other isekai, and while the early translations were MTL and slightly difficult to follow the recent improvements have really let it shine.
While it says 'Karate', it would be more appropriate to say a Karate based mixed martial artist. There is De Le Jiva, Rear Nakeds, and a wide series of various grappling moves mixed in with his knockdown style of karate.
It takes a hyper realistic approach to 'what if an MMA fighter was sent to a low-fantasy universe'. Well, he'd 'Mata Leon(Lion Killer)' demonic dogs, apparently.