Okay, I went to the trouble of borrowing a relative's 4G connection in order to take a peek at this event.
...It doesn't seem all that different from the way Japanese events are handled, to be honest.
Note that some youkai are worth more points than others:
Enma Daio: 10 points
Hihi: 15 points
Daikokuten: 30 points
Shuten Douji: 70 points
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...These connection timeout errors are really annoying...
Hm, are youkai that are at the end of their own daily maps generate points same way youkai added at the beginning do? Meaning, can you spam, say, Shuten Douji's daily for additional 70 points per?
From what I've read, no.
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There's a feature I read about that I think might be implemented already:
Each day a random story mode map will have its stamina usage halved until the next day. If it's active here, then that provides another option for farming these "invading" youkai.
Halved cost of a story stage was on since day one I think. Never knew if its random, or what, cause most times I saw it on it was dark or light stages. But that is it, its for story stages, not event stages - thus doesn't help us, cause at least from what I understand only stamina burned on event maps works.
That is correct though even with the half stamina story maps I am only getting the 10 point senkai once working out at 50 points per 25 stamina, which is less than my average on the hell maps (being 60). Seems the more stamina you use the better chance of higher points.