Seihou - Banshiryuu C67 - Perfect Lunatic Stage 4A (NMNB)
5NMNB. Calling it Stage 4A to distinguish it from the Stage 4 in which you fight VIVIT instead. :P
The boss fight against the shrine maiden Hirano Sakurasaki is pretty damn tough to NMNB; fast bullets combined with RNG make her hard to read at times, especially during the final pattern. That was the main nuisance for me when trying this. A lot of derping happened too, but still. I've had to try this for.. I think about 6 hours, maybe? Very long, yeah. Rip. I also managed to not NMNB it even when playing it non-stop for 4.5 hours... X_X That final pattern, argh! xD It got me every time. Said 4.5 hours happened during a Skype call though.. and I'm pretty bad if I play while talking.
I had always thought the blue aimed lasers in her opener pattern were impossible to dodge, but a friend got me the idea to try different positioning, which led to me finding out a way to dodge it. c: Now I actually think it's Hirano's easiest pattern, lawl.
I dealt as much damage as possible after that in order to skip the second SE, which can have a pretty mean RNG.