That said, with my ship, Tezuka/Ryoma, it's almost impossible to find good fic that doesn't spoil major parts of canon
Tezuka/Ryoma: Must-Read Fic Recs for the new PoT fan.
If you're exploring this ship and don't read these I will cry.
Tezuka/Ryoma recs - Contain Spoilers: you should not read these until you are done with the series. And then you should. Because they're amazing.
Tezuka/Ryoma recs - Spoiler-Free:
NO I TAKE IT BACK. IF NONE OF THEM DO IT FOR YOU, I WILL REC MORE. AND MORE. UNTIL YOU FALL IN LOVE AS I HAVE. :((
Also, I should mention I have over 200 fics in my memories that are all pairings of Tenipuri. But which are mostly TezuRyo. I haven't vetted any of them for spoilers, though, so you'll have to trust the author to warn you, which, sometimes they don't.