Questionable Questing

Way back the E3 commercial for it was needlessly edgy and had the MC repeated the lines kill CHAOS several times so it became a meme.

This Final Fantasy Judgement?

I think so, never played it wasn't the biggest fan of final fantasy, but back to your idea. What's the evil or shall we say good empire your MC is facing?

Multiple different Kingdoms descended from a good King who originally sealed the great darkness but have now fallen into separate realms with a divided religion

What's the backstory of the mentor figure? Hidden son of the original king turned demonic champion and avatar? Maybe he had a hand in the splintering of the kingdom due to the lack of a strong heir? Is the MC going to have a family to seduce?

You could also have the king have a few surviving lines, maybe through his cousins or siblings, and their descendents are all claiming to be legitimate through their connection to the king. All of these different lines ruling different regions and busy with a game of thrones style political bloodbath as the once powerful family splinters apart, egged on by the MC and his mentor in the shadows.

Yes family to seduce and by the way want to talk incest harem theory about why it is such a common fantasy.

I love that idea of multiple lines

It's a common enough problem for big empires, lord knows everytime Roman had a "great" emperor, the succession crisis afterwards that has every member of the distant family have a battle royal, made sure to fuck things up.

But incest harem theorizing sounds fun, lets hear it.

So

There's a trend of guy surrounded by hot sisters and mothers and aunts as a natural breeding harem that loves and lives with them. It's like a primal porn fantasy.

It's freaking weird

Well it depends on how much you want to look at it. The thing you have to realize is the influence that visual novels had on porn and early fanfiction in general. And these visual novels, where made previously because it was easy and there wasn't a lot of coding. So a lot of times people made pretty realistic and mundane settings. Like a highschooler. You see where I'm going with this. lol

When people inserted themselves into the characters, they obviously didn't have any family bond like the main character was supposed to, and since a lot of times family members where the first one put into the game they had the most time put into making them look good or have a distinct personality. Which means fans of these original works, when they made their own added in some more optional romance targets.

Ripple effects

Optional targets the previous author probably didn't consider. lol. Then as time went on fans of these works like the taboo nature of it and expanded it to include even more family members, Until you have a healthy ecosystem full of incest. lol

The no need to woo or risk rejection. Ready built wives that already like you. Extremely delusional

I'm back, had the last slice of that pie I bought a week ago. Still pretty tasty. But, I think another angle is daddy issues. Or mommy issues I don't judge. lol. But no seriously, I do think a lot of people don't have normal family's or relationships so the fantasy of a super loving comfy family is nice, and the more sexual parts is just a way to channel some of that anger or frustration.

Adult brain mixing with old issues

Plus it's just the nature of porn. If you're really into it, like multiple times every day, then it kind of hard wires your brain like an addiction and you need more crazy stuff to get off. Just step siblings isn't enough, you need the whole incest Buffett. Just one spank isn't enough, you need a whole whipping session. Just one foot sniff, you need a whole tongue massage. You get the point.

Shit just starts to escalate.