I mean, I know it's in the title, but it still needs the Futanari tag. The people that like this stuff should be able to find it that way in the future after it gets buried.
There are ways this could have been more effective NTR. First of have the guy she is cheating with be a established loathed character, like Floch Forster. Him getting to father Historias child would really sting for the viewer. Secondly no one cares about the guy she is currently cheating on. So have Historia be haunted by the memory of Ymir and Eren, the two true loves she feels she is betraying.
Can one NTR a symbol of monarchical power? I don't really feel any love/marriage vibes on either end of Farmer-kun and Historia's relationship until after she gets pregnant (After she starts fucking Master-san?), but it still gives off that vibe, as though he managed to cuck the crown itself.
Art: heavens gate key/10
What about the tags?