The art is great, the world building is varied and inspired, and this story's equivalent plot of fighting the demon king is honestly well done, with a lot of amazing character interactions and interesting characters.
But there's one major flaw, and unfortunately this flaw is related to the main character's motivation: The author keeps regressing the progress of the relationship of the main character and the first wife.
Worse than that, it causes the main character to intentionally start ignoring his other wives.
This causes artificial, implausible and nonsensical tension because the other wives want their turn and are forced to wait. This tension causes the first wife to feel insecure, causing the main character to always hold back until she goes so far he takes a manly stand to show her she shouldn't be insecure, and then progress is made.... And then the author forces their relationship to regress, but with the caveat of the other wives becoming more impatient and competitive as a result, making the next bout of insecurity worse.
And this situation is made worse by the fact that:
THE PREMISE OF THIS STORY'S PLOT IS FOR THE RING KING TO INCREASE HIS POWER BY INCREASING THE DEPTH OF HIS RELATIONSHIPS WITH THE RING PRINCESSES.
Literally, the plot requires the main character to have a harem with 5 women, and it requires they all love each other as deeply as possible, otherwise the abyss king wins and the rest of the world dies. But the author is forcing a nonsensical monogamous romance into this core of the story and it's poisoning the rest of the story.
It feels like I'm reading the same nonsense reasoning as the Hegelian dialectic... and now that I think about it, that's kind of what this is: I want two opposite things at the same time, so let's force them together until some magical compromise or evolution is discovered.
For this story, the opposites are harem and monogamy (where a person having one automatically disqualifies them having the other). The author seems to want both at the same time, so they write both happening at the same time and hope a compromise or evolution is discovered along the way. And the results?
Plot holes, a underpowered MC, and tens of thousands of extra deaths that didn't need to happen. Just like the eventual results of IRL Hegelian dialectic, interestingly enough (over a hundred million deaths, really; if you know, you know—it's a long explanation of how, but if I were to give an oversimplified hint: "Struggle session, anyone?").
Basically, since the relationships of the main character and his wives is required by the plot, and the author keeps refusing to fulfill those requirements, it means most of the actually good writing happening outside of said relationships is wasted.
Honestly, the pretty art and the desire to see how this train wreck unfolds is why I'm still reading this.