Nah it actually does happen a lot, unless the game has extremely strict timegated contents you almost always get a few huge swipers that completely outgear everyone else. Gigantic day-1 guilds are also very real, mostly people from an already established community.
I kinda forgor the lores for the oni tribes, was it ever explained why their princess have human blood? Did their queen simply fell for a human or did she get, you know, r-worded, by a human during the war or something?
This isn't the last arc, this chapter is currently depicting the 1989 Arima Kinen, and I know it's weird that I have to spoiler tag real horse facts but
He didn't cross the line with the stepsister, only fucked his blood-related girl friend.
As Yuki once said, incest is the best when they're blood related.
Technically she's a fake childhood friend so this doesn't count, they first met in high school.
I wonder if editors looked at the script and saw "childhood friend winning" then immediately decided to axe the series