We're up to 6 episodes right now and I can say this anime is consistently beautiful and lively show. Something you don't see from a lot of animes with great pacing to boot. It is rare to even find an anime that made me want go out of my way to read the manga. Also finding there is a Light Novel to read and you can see from the manga it heavily improves apon the source showing how anime should improve the source.
Ok let's get on to the main character in short are very expressive and a joy to watch. Rimuru's voice fits perfectly and for a slime it's(slimes are genderless) expressions are pretty wide for a slime. We even see how Rimuru effects the world and how he interacts with others. Also just to note It's an overpowered protagonist but isn't the most powerful in the land yet.
The comedy elements work very well when melded with Slime's story and characters but remember comedy is subjective so not everyone will interpret it the same. From my experience it had me laughing out loud at certain adult jokes and character facial expressions. Other characters definitely have their momments and the interaction between characters are just great.
This may be a light heart comedy at timed but it can get dark. From some isekai I've seen it can be hard to go from light to dark moments but slime pulls it off without out it hinder the anime it's self anymore and I would get into spoilers.
In conclusion, That Time I got Reincarnated as a Slime is a joy to watch. The animation and voice acting improves apon the source material. The characters interact well and in themselves interesting. It can get dark at times and does it well. I also hope you all will found this review helpful and enjoy the anime as much as I have.