This is all going to be super rushed! So I'll keep updating constantly! But what we do know:
Miu is Miku's daughter and Miku is in the game! She went missing when Miu was 3. Still voiced by Rika Wakusawa. There are rumours that she is currently at the mountain, but why?
Onion's name is Shiragiku (白菊), voiced by Natsumi Takamori. She is notable for her white hair, and seems to be able to read people's minds. She shows up at the shrine, whispering mysterious words to visitors. She has a faceless doll called a hitogatami (人形見), but what does it mean...?
Haruka Momose who we met on the website. She's Fuyuhi's friend and is easily swayed by others' opinions. She seems to have a secret between her and Fuyuhi, which may have something to do with her spiriting away.
Watch this space!
Mt. Hikami Cable Car, a cable car built to stir up tourism at the mountain again. There was a big landslide soon after completion and it was abandoned. Rumoured to be a famous ghost spot where ghosts are spotted in the car, etc.
Watarai Mansion, a house where a folklorist called Keiji Watarai lived when he investigated the mountain. He went missing while investigating the religion and the house suddenly vanished from the mountain. It's rumoured to have been spotted amidst the fog.
Katashiro Shrine, a shrine in the centre of Shirazu Forest with a lot of dolls. It's been empty for ages, and no one knows why the dolls are there. Kids' ghosts play there, the dolls talk, and a girl with white hair and a doll stares at you, so the rumours go.
Tunnel/caves, which stretch beneath the island. The mountain was seen as the human body and the cave thing seen as the inside, where water (and gods) dwell, so it was called the... womb cave? Sounds familiar...
Hikami Tunnel, a tunnel that was built with the intention of ferrying tourists to the top of the mountain. Water from the caves flooded the tunnels during construction and many workers died. construction began again later, but the entire mountain was abandoned, so it was closed down.
Bathroom, where Yuuri meets a ghost!!!!
In terms of gameplay:
Wetness - comes from rain, taking attacks, being in water obviously etc., which fills the wetness meter. Wetter you are the stronger your spirit power is, other powerups to the camera. OTOH, your defence lowers and you encounter more ghosts, so it's risky. Wetness clears up over time, but if you want to fix it right away you can use the "purifying flame" lantern.
If you take an attack from a ghost in "yomi nure" status, you too will enter it, which lowers your defence and gradually your HP too, as well as messing up your vision. This too can be cured with the purifying flame, or you can defeat all ghosts, leave the area, etc. Up to you.
Also, if you touch a ghost as they're "dying", you can view a past scene of how they died. You can also touch them during special attacks. If you're successful, you can beat the ghost regardless of their HP. Most ghosts are unique with their own past, and you can form a sort of "collection" of these death videos.