I wasn't aware of that, and haven't tried ASWS since it's tagged with NTR.
How many are mandatory for ASWS? In PQ only 9 are (currently) required for the Main, 10 if you include Qetesh. Plus three more you don't have to pursue past a certain point. The others are entirely optional.
Tower: Erevi, ED, Imp, Venomina, Naamah
Temple: Ziva, Caleah, Julia, Alice; maybe Qetesh
Limited: Beth (up through the date), Liandra (rescue her from the Grumpkins...you're going to need sacred water for EFPs if nothing else), Maghda (never have to see her again after getting Edgar's stuff)
If you're using Cheatmode you don't have to meet Liandra at all to complete the Main, but most players do her content anyway. (Technically you don't have to sacrifice to Naamah after her quests are over but I suspect that would be a bad idea when the Main storyline conclusion happens...)
I went a little more in depth about the NTR above, most of my saves have 0 NTR, and I put the switch on just in case. In reality it isn't really NTR. It voyeurism reward for the player. Punishment for the MC, but only because the player chose to punish the MC. And the dev takes the being able to turn it all off pretty seriously. Recently a player found a scene that can be triggered after you take five steps (that you would only do to get an NTR scene) even with the NTR switch off, the dev patched that out immediately.
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The mandatory is kind of tricky, because it works differently. A lot differently. None of them in ASWS have to be pursued to get to the story end, but more so than PQ, ASWS quest content is tied to fully unlocking the LI's. The gates on progression and opening of new LI's are tied progressing LI's, but that is pretty much just the courting stage. There are a few exceptions.
It is worth knowing, there isn't special pastries or aweing, what there is the MC's super natural cum. It turns LI's into sluts. Most of the courting is working your way to getting head, once you get it in her mouth, you can repeat that until the LI is fine with your fucking her mom in front of her.
Mira you pretty much just have to kiss her (she was initially designed to be the MC's sweet heart, but she has taken a back seat as the story has expanded) to unlock every bit of her content. But that also means taking a more noble route, during a major point of change in the game, you would have to side with the church.
When siding with Syfa a succubus, is the much more fun route, to get the Syfa end, You have to fully corrupt, Mira, Bridget and Heather.
So in just that instance, you don't have to court any LI's to get to Mira's current end point (after getting Mira to kiss you). But the fuller fun gameplay end means you have to court three and get Syfa for free.
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In order to get your house upgraded, you either have to knock up Mira's mom, and build her an orphanage. Or get the prudish farm daughter to fall in love with enough to give up her vag virginity. (She gives up her B hole pretty easily). After she falls in love with you you can renovate her farm. Either renovation of Emily or Penny, allows the MC to upgrade his house.
This is one of the few instances where you have to fully unlock an LI to get the reward associated with her.
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There is a witch that if you fuck a whole lot, like a lot alot, I cheat it, but it's like 15 times, you can start to get magic spells. The spells are one way to complete some other difficult tasks, but not the only way to complete them. The witch isn't as bad as Ziva in witch form but close, a lot of players skip her. I don't because the spells are handy and fully unlocking the witch opens up her sister to being a maid for your house.
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So really you can skip any LI, you won't get as cool rewards, or as full as an experience but if you don't like an LI, don't court her.
Their are some progression gates, but they are more story quest then LI romanced unlocks.