May I suggest some of these fics from different fandoms. Now these ones I enjoyed quite a lot but it depends on you if you'll enjoy it as well.
Overwatch:
Impact Factor - Mercy/Pharah, good character interaction and build-up in the romance. Still on-going but it is enjoyable nonetheless.
Birds Among Dragons - Mercy/Pharah, now this one is actually a cross-over with the one of the Elder Scrolls game, Skyrim. Action and adventure, enjoyable. On-going, a bit fast-paced but it's exploring their relationship as well.
Frozen:
Draje Hjerte - Elsanna, now I'd say this is one of my favourite Elsanna fics out there simply because of how their character and romance builds up and the plot is good as well. On-going.
RWBY:
Acceptance - Pyrrha/Ruby, the great thing about this is that, perhaps it is slow-burn in a sense, it delves into both characters feelings and emotions and how they come into terms with them from what I have seen so far. This is on-going as well. It's an enjoyable read.
Winds Of War - Yang/Weiss & Blake/Ruby, one of the most action-packed, romance, and angst fic I've seen thus far. Complete, I don't want to say too much but it's really good.
As for Mai-HiME ones, I suggest works from ShayP, various chapters of her fic are extremely long and enjoyable. As for other Mai-HiME fics here.
Magical Tomes - ShizNat, HP x Mai-HiME. Need I say more? It's still on-going.
Of Impulse and Fey - ShizNat, writing is great as well as the plot. It's really good and has a normal pace with both the story and the romance in my opinion. Completed
The Midsummer Chronicle - ShizNat, one of the fics I enjoyed that my friends had made before they passed away. This was initially inspired by Fate/Stay Night. Completed, english isn't so bad.