Touhou Emblem Chapter 18 - Invaders from (former) Hell
2So first Embodiment of Scarlet Devil, then Perfect Cherry Blossom, Imperishable Night, and then Mountain of Faith, and now Subterranean Animism. I think we got a pattern here.
However, this doesn't straight up starting to go to the underworld despite what would anyone expect. The first part will begin with repelling those who want to get revenge away from the Human Village.
Speaking about this, there is reinforcement spam by the way and the additional enemies aren't too much problem. This is just a good old "survival" chapter, just with promoted enemies being so common.
Not much I can give but you'll need to maybe spread your forces a bit. You'll just need to be careful with which enemies you're baiting. A promoted Alice will even do so much better at baiting enemies one at a time - though your stronger tanks can just bait multiple at once.
By the way, here's one difficult choice you'll have to make, you either would keep Keine and Komachi all the way to the endgame - two prepromotes, one can shift between Cathrapact (the game's Great Knight) and Sage - essentially making her a mixed physical/magic unit, while the latter is a Berserker with Lethality (so this probably explains where did the lethality skill go to, and yep, The Last Promise's Liquid style.) Or you can abandon them after this chapter and get Yuuka, a prepromote Spearmaster with ridiculous bulk and hitting power (but slow), who also comes with the legendary S-rank spear weapon, the Tonbogiri. And no, she doesn't drop it, if you end up killing Yuuka, you lose it forever (but you get to keep Keine and Komachi for the rest of the remaining chapters). Sadistic choice indeed. And not to mention Yuuka moves if your unit is in attack range...
To recruit Yuuka, have Marisa move into range and talk to her. This can be easier to do if you deploy Mystia in this chapter (but I didn't)
Keine also causes a game crashing glitch if you try to shift after she cantos in Cathrapact form. (I'm pretty sure it'll be fixed in the upcoming redux version of Touhou Emblem.) So just don't.
I don't think some people will be happy with my choice of obilerating Yuuka, but I'll do an alternate playthrough with replacement characters later (possibly), and if I do, I'll have to recruit Yuuka for the replacement characters run. I already have three good tanky units (Suika, Alice, and Mokou), thank you.