So my group has been playing Season of Ghosts, in Japan, matching story beats to IRL calendar for almost one year now. We started on the summer solstice last year with the Reenactment Festival, managed to line up the events so that we started book two on the autumn equinox, completed the monastery and began book three on winter solstice, and are almost certainly about to end book 4 one week before summer solstice, so we will have a five years later recap session on the summer solstice. This adventure tapped in so hard to our local environment, customs and presented us with deeply thematic horror and moving moments as Willowshore became our home. I have had to do very little to no work as a GM to bridge inconsistencies or bring the events to life, we've skipped almost none of the content (players skipped a few rooms in the bigger "dungeon crawls") and I've almost never felt compelled to add content, although there was of course some adaptation due to the players' backgrounds and actions interacting with the story. All that to say... BRAVO! There are no words to describe how awesome this adventure was for us and our group... except for the closing chapter.
So... here's my take on the closing chapter of this adventure:
Kugaptee's Willowshore is as described in the book but empty... deadly silent except for the occasional fluttering of the crimson moths of Kugaptee. A trail (made by the killer of chapter 2) leads the party to the home of one of our party's characters... there's a cave leading under the hill of the Great Willow and this allows the player to reveal a secret to their background that they've been hiding before we finish out the campaign, but also, the cave walls have been defaced since what that character knows they should be... deep under the hill, a fog surrounds and they emerge...
Final fight 1: Summer... Gurglegut was far less interesting of a fight than Zoudou, so she's there at the altar about to sacrifice... not a child but the chained spirit of Kazuma Oono (who was murdered in our play of chapter 2, but in our case is also the grandson of one of our players...) All of the stats were buffed to current level by adding 13 to all of her d20 target rolls and giving appropriately scaled up spells (minions had her stats -2)... at the end of each round the big stomping sound beyond the wall of ghosts pounds against it and actually an arm of kugaptee smashes through the wall of ghosts every other round (Basic Reflex DC 39 6d12+33 << the hazard damage/DC taken from GM Core) after defeating Zoudou the claw of Kugapteee retreats, they can try to help Kazuma to remember, and an opening is there in the wall of ghosts
Final fight 2: Autumn... mystery tree is not an option... we push through the wall of ghosts into the root chamber below the Tan Sugi Monastery and face off against Xin Yue, stats buffed to present... in the fight another Kugaptee claw hazard from below. Rather than help from Zhi Hui, it is a manifestation of Tan Sui-jin that assists them. Held prisoner for sacrifice here is You So-jin (also murdered in chapter 2, since they were able to guard Elizeth very well) ... the opposite side from where they enter this root chamber has a gate to the Karahai garden...
Final fight 3: Winter... the Karahai central garden, stripped bare of trees... lined by exorcists converted to follow the Kugaptee cult. standing center waiting the party is Fenfang (who our party uncovered as the Kugaptee agent, they also made peace with Mago Kai rather than fight so the Mago Kai as written didn't work at all) ... when challenged her body twists, throat slits, head falls off and we have the original adventure's showdown against the Argyrzei fiend but with the addition of a Kugaptee Claw hazard... in this space they rescue the emaciated form of Ol' Matsuki, who was exorcised and disappeared from the mindscape during the winter months of our game. Exiting the opposite gate to the garden, they find...
Final fight 4: Spring.... we didn't fight the path maidens... actually it works to just go straight to the governor's mansion as described with eyes, etc., but have them enter the central courtyard to find it full of bodies. Faces familiar and yet different, like the grandchildren of the willlowshore population they know, seeming to have committed a mass suicide. The shisagishins are there as written, and the encounter with Heh and the aftermath are as written.
Conclusion: they leave the manor through the door in the governor's quarters, drawn on by the sound of a flute... they are in the Tan Sugi Monestery by the great cedar. The flute is being played by Zhi Hui (one that has never met the characters) but more interesting is the scene around the Tan Sugi cedar. An axe embedded in its side leaking black tarry sap. The yard containing four or five bodies of Mago Kai loggers that have been left unburied for close to a year, and the broken body of Ugly Cute, roughly hewn by loggers... fireflies gently carried on the wind coalesce into Tan Sui-jin... she bows to the party, smiles wordlessly, an looks at the axe embedded in the tree before another breeze causes her form to revert to the fireflies... scene fades to black with the haunting sound of Zhi Hui on the flute... and then we pick up at the summer solstice festival in Willowshore five years later... players tell us what they've been doing, and help me narrate the changes to Willowshore, and especially the new way the festival is held in Willowshore