I'm already a huge fan of the isekai genre, but this gem of a story has a particularly refreshing main character. His- well, character- is so very polite and generally well-mannered and -intentioned that I can't help but root for him to succeed! It definitely warms my heart that the supporting characters also appear to care for him sincerely, so you don't end up with the heartache of watching a such a nice kid suffer through life. The personalities and interactions are crafted well, so the adventure flows really smoothly for me.

Update: It's ok. Its just Mary Sue Mc Isekai.

OLD REVIEW:
So this one I like so far. It's got nice characters and I enjoy the running “Misunderstanding the main characters past” joke that they have. I like the MC, he is reserved, kind, and respectful. There are too many Beta male MCs or Kind Marry Sues in Isekais nowadays. So he feels like a nice change.

However, the manga only reaches the intro stuff in the LN/WN. But the WN apparently starts off very strong but after the first book, the writing quality falls off and becomes very poor.

Hopefully, this doesn't happen here. So for now, I'll give it a good score.

EDIT: It's been a year and the manga had progressed much further. So I'm gonna be updating my review. So far my thoughts are mostly the same, though I will agree with User tiankioo's review that I was wrong about the MC. I regret using the term BETA MCs as an example. The MC of this series is just a Mary Sue like all the others. I'm still a fan of the running “Misunderstanding the main characters past” joke.

There is another reviewer that complains about the worldling. The world-building is no worse than most other isekais, I'd argue that the author has put more thought into the world-building than other isekais of the same quality. However, there is some BS about why the Tamers Guild is too stuck up its own ass to ever acknowledge the MC's world-changing discoveries. At this point, they are just bout to enter the arc in the Web Novel that killed the series for most readers. I'll see how the story progresses from here on.

This is a light-hearted little feel-good isekai, it's full of fluff and scenes with sparkles everywhere. Don't go in with your expectations too high or you'll get disappointed like some of the other reviewers.

... Last updated on June 10th, 2021, 4:46pm

It certainly is a SoL, quite peaceful and suitable as a lighthearted read.
Overall, everything about this series is quite decent, neither bad nor outstandingly wonderful, except for the art, it's chef's kiss beautiful (and I'm a pretty picky one when it comes to art). And although MC is a Mary Sue, he's still a pleasant character, just kind and polite, not at all naive like a white lotus.
Until this point in the manga and after over 1.5 seasons of anime, there's still nothing in particular I dislike about this series. I've not read the novel, but as it was said to decline over time, I'll see how the manga goes from now

I dont mind SoL I dont mind RPG theme, and I don't care about isekai.
But this manga takes the cake for being one of the laziest plot convenience I have ever seen, the MC is blessed with plot weaving power through the power of his slime. His power just seem too flexible he can get out of any situation and most character just worship him like love at first sight. Even in a SoL manga, conflicts, and inconveniences still exist to explore the MC further, but this one just have the writer work his plot magic for him.
This manga is fine if you just want to turn off your brain to only enjoy the fluff, because it is incredibly safe, to the point that bored me.