This is a fight that comes in 2 phases, separated by a short cutscene in between. You have to do them back to back so if you mess up, you've got to redo the whole fight.
This fight uses a map mechanic, where you can shoot the lamps to prevent certain attacks from coming, but as a Solo character, it's not word the AP cost to do so. Especially with how behind we are on speed, You'll never get any meaningful damage in. So I choose to ignore the fight mechanics and just brute force my way through it.
The first phase is pretty simple. It doesn't take a lot of attacks to end the fight. I did take a couple of tries to get a hang of the parries. I opted for Healing Parry here. It's a pretty handy tool to keep yourself healed.
Phase 2 gets a lot trickier. It feels like he's getting 3 turns for my every 1. The attacks are also much more difficult to parry, for me at least.
Sciel would have probably been a better choice for this fight, as she has Dark-based weapons, which I assume is it's weakness. However I wanted to use Gustav for reasons.