It's not that lecherous, but it does seem a little lame. Of all the stumbling blocks, they need to pull out light-magic ropes? And that's pretty much it?
When it was revealed one of his Unique Skills was literally "foresee all steps necessary to achieve any goal," I checked out. If he can simply isekai-THINK at a problem and solve it, where's the challenge?
I enjoyed it from the start, but as he became apocalyptically mad at the treatment of slaves based largely on his personal experiences on the battlefield, I knew we'd hit peak.
I also appreciate multiple characters with frailties and disabilities. Eldan's a really solid dude. Even with chronic...
If the solution to the villains' problem (you) is poison him or something, that they never do is baffling. "Oh, but I'm the safest in the Stadium, everyone would suspect she killed me!" Motherfucker, it's widely known both the Master of Ceremonies and principal owner are involved in every crime...
And just that, he only ever fucks them for three days. This process convinces them he's the best guy ever, above all men they've loved including those currently, etc. etc. etc. It's all so tedious.
If it's a new female character, 9 of 10 times he's going to fuck them for three days. That's it. Those are the stakes, that and only that. It's a long, drawn-out rendition of "TRYING TO FUCK." And when he's not doing that, it's battle sequences in which he does Gamer at it and always wins.
You...
"Oh no, I just can't resist the magic restraints she's begun to use all the time," right. So his Copy ability becomes a huge liability if he copies any power, ever. All to justify 15-year-olds getting into magic bondage.
Buddy ... you'd have to be extremely stupid to attempt legal marriage more than once concurrently in any US State. That's the broad definition. Sexual cohabitation with any number of people could fall under common-law marriage, but in practice it'd be far more difficult to prosecute. It's why...
On one hand, it's flimsy pretense for sexualized fanservice.
On the other, it's very funny seeing an entire cast terrified of their own sexual drives and the prospect of romance.
Enforcement practically doesn't exist in the United States. Seattle and Utah have enough poly configurations that calling the cops would make you the asshole. It'd probably be fine, especially in a world where male-led harems seem to be the default.