There's gonzo kink and cleverly kinky. Missa X opts for the latter in this unusual but satisfying on its own terms faux incest story.
Lyra Law projects just enough strangeness to be believable as the protagonist, welcoming a medical exam from her stepbrother, who's been recently installed in the profession. She becomes suspicious when his technique becomes quite sexual, but soon some fingering and dilation by speculum leads to orgasm and outright humping, with orgasmic results.
No surprise in a Missa X opus that the climax is a creampie. The kinky elements only add to the fun.