(Why does Youtube mess up the start of the video? :/ )
I finally had a reason to do a new run of this game, and it's a massive improvement over my previous score of 1498 million from last July. This run puts me in 4th place on Royalflare (and 101 million points behind the current world record).
I spent a good portion of two days working on this. There were a couple early runs that got ruined right at the final boss (a single death is catastrophic in terms of score), and then later runs went even worse, but in a way I'm glad it took some time to finally succeed, since I made plenty of improvements to my route along the way that added at least 40 million points to the overall score. (The first run might have gotten 1.53-1.54 billion if I hadn't died three times (!) on Kanako.)
The stage 4 performance was rather poor--one of the worst among the attempts where I didn't die on it. My stage 4 strategy needs a complete rework anyway, since it's possible to get 50000 more faith on it than I did in this run. However, the rest of the stages went very well. Stages 1 and 2, in particular, went as well as they ever have for me. I was quite nervous on the last stage, and it shows, but I managed to not mess up this time. Hooray!
If I ever come back to this game, it'll be with a new stage 4 strategy (in addition to a few small improvements throughout), and I can easily see myself getting another 50 million points.