Nitori Kawashiro got me. It turns out her shotgun attack during her first spell card changes its angle on the last shot... sometimes. So even if you're safe from the rest of the attack, the last shot can get you... sometimes. I swear that wasn't the case before, I've gotten past her a few times pretty recently and I don't remember that being a thing.
Nitori's my favorite boss I've seen in Touhou so far, thematically if not for the actual patterns or the music. I love that she sneaks up on you with optic camo... after you've already seen her.
TH10: Mountain of Faith.
Follow-up, I did check this out and... Jeezum crow O_o I may be rusty, but I'm pretty sure this is a lot harder than 7 (the only other one I played). It did get easier once I figured out the new bomb system though. Here, it drains your attack power... which means you can bomb more often, but your normal attack gets weaker until you collect replacement powerups.
Also this is *probably* just me adjusting, but it feels like the "threshold between life and death" is practically gone! That time after you get hit, where you can use a bomb and survive. Particularly since I'm playing Reimu, who had extra time in 7.
Long story short I restarted the first chapter about 10 times until I felt like I had the hang of things. Nitori fight was GREAT! I sang along to these lyrics:
https://www.youtube.com/watch?v=kgYxe6oNJKUI just managed to survive, only because she gave me an extra life in the first stage (:
Then a Tengu "went easy on me" and I ded
Though apparently I was taking too long (bombed away my attack power), the timer was counting down... actually showed 00 when I died. IIRC, that would have ended the fight in victory Dx
Touhou 10: Mountain of Faith