I gotta say, I think a lot of folks miss the mark on this one. Takiya and Fafnir from 'Miss Kobayashi's Dragon Maid' aren't about dominance or submission in a typical 'power dynamics' sense, which is what usually gets dissected in fanfiction. Honestly, it's way more subtle. Fafnir is an ancient, immensely powerful dragon, but in their modern dynamic, Takiya holds the 'power' because he's the one acclimated to human society. He's the guide. Fafnir might be a terrifying being of legend, but he's utterly reliant on Takiya for understanding video games, figurines, and how to order takeout.
The fanfics I've enjoyed most play with this inversion. It's not about who could win in a fight—we know the answer. It's about Fafnir learning to navigate the mundane world through Takiya's patient, nerdy lens, and Takiya having this casual, unfazed power over a creature that could level cities. The 'power' is in Takiya's quiet acceptance and his ability to share his passions. Fafnir's 'weakness' is his fascination with it all. That's way more interesting to me than any clichéd battle for control.
You see this in fics where Fafnir gets weirdly protective over a limited edition game pre-order, or Takiya gently explains internet etiquette. The dynamic is built on mutual fascination, not force.