Well, I finished the first Lostbelt. Used my Command Seals on Anastasia, which I kind of regret. I mean, losing the seals wasn't an issue as I beat the final fight quite easily, but I could've won cleanly if I rearranged things a bit and used a different Mystic Code if I was willing to lose that 25 AP.

Other than that, I thoroughly enjoyed myself. The climactic battle is pretty memorable and well setup, they've established a scenario similar conceptually but different enough from the Singularities that there's a lot of room for what they can do with them - as it's more Sliders now and less Nasu-verse Doctor Who - and it's just cool to have a human adversary.

I was watching a Youtube video a while ago about video game rival characters - like Virgil from Devil May Cry - that having an adversary which mimics your own skills and other recognizable aspects of being the PC is the closest you'll experience to PvP in that kind of single-player game experience. This is intended to give you the illusion of facing and defeating your - from a certain perspective - peer, rather than a more scripted experience against the computer. I think that's somewhat at play with these enemy Masters, or as much as you could do in FGO at least. Actual PvP would be a nightmare, as Learning with Manga suggested.