MAR Demon Soldier Legend BG fanfic, HE, first person
Original female protagonist, male protagonist Phantom
It's not a time travel, and if you haven't seen it, it doesn't matter if you treat it as an original Western fantasy.
Notice! ! The MAR fan here is the comic version, not the animated version.
The difference is that after the final battle in the animated version, I can't refer to the entire Phantom character design as OOC.
(This is an unpopular old comic that shows your age. I just love villains)