WoH: Mysterious Mountain of Missing Men

Mystery: Mysterious Mountain of Missing Men (general story and mystery title provided by a friend on different server)
You hear a rumor that somewhere outside Shiokawa there's a mountain where young men keep disappearing. Reportedly, they travel there after suffering sleepless nights and hearing a call of a beautiful woman coming from within Mountain 000...

[Extra Mystery Actions] Take Notes at School's library x2: You read many stories about monster women and eldritch beings, who lure young men with sultry voices and enchanting songs, only to kill them and feed upon their corpses. Is this what is happening at the Mountain of 000?

Start: You've heard that another young man has disappeared, and that he was last seen in Shiokawa Docks.
Investigation 01: Seaside: The dock workers do not remember seeing the boy, but they know a bar that is popular amongst young men and senior students. Maybe someone there heard him say anything.
Investigation 02: Seaside: A young sailor tells you that he heard the missing youth mention that he has just recently graduated from Shiokawa High.
Investigation 03: School: One of the teachers remembers the boy. She mentions that the boy's parents are living in a mansion at the outskirts of Shiokawa. A visit there should prove fruitful.
Investigation 04: Mansion: The boy's parents are on vacation to Okinawa, but fortunately, you meet the old lady who works as the groundskeeper. She recalls that the boy spoke often about Mountain 000 and 'the beautiful song of a woman'. She tells you that Mountain 000 is somewhere near Village.
Investigation 05: Village: The locals mention that a lot of young men have been passing through recently on the way to Mountain 000. The local priest knows the fastest route there.
Investigation 06: Village: The local priest tells you the path to Mountain 000. It goes right through Forest.
Investigation 07: Forest: You enter the Forest. According to the Priest's instructions, the route to Mountain 000 is quite long...
Investigation 08: Forest: You've been climbing up for some time, and the trees are getting sparse. You must be close!
Investigation 09: Mountain 000 (special icon): You arrive at Mountain 000... wait, is that a cave entrance up there?
Investigation 10: Mountain 000: You keep climbing Mountain 000 toward the cave. It's drawing closer - soon you should learn the truth behind the disappearances.
MOUNTAIN 000 EVENT: You shiver as the cave entrance is littered with human bones. Despite sun shining brightly, the cave is pitch black just few meters in...
Option A: Get the hell outta here!: You run away, hurrying to alert the authorities about the macabre findings at the mouth of the cave. [ENDING A]
Option B: Move deeper inside: You move deeper into the cave, when you suddenly start hearing a woman's voice! She sings beautifuly, inviting you to enter her loving embrace...
>>Option B1: Get the hell outta here! (same as Option A)
>>Option B2: [FLASHLIGHT required] Turn on the flashlight: What the-!? Instead of a beautiful woman, you see a grotesque cave wall, shaped like a beast's maw! Its flesh is pulsating horribly, and the rows upon rows of shard-like teeth spiral toward the throat of the beast, fleshy tendrils hanging from the ceiling. The tongue trashes along as the song intensifies... you struggle to keep your thoughts straight!
>>>>Option C1: Struggle: You struggle, tearing at your hair as you shakily step away from the monstrous maw and back toward the cave's entrance. You feel your sanity slipping, but soon enough you're free from the song's dreadful influence. You must warn the people about the tunnel monster! (-2 Reason, ENDING A]
>>>>Option C2: [CAN OF ACID required] Throw acid at the fleshy maw: You decide to end it now. You open the can of acid and throw the corrosive at the maw. The song abruptly turns into a pained shriek as the acid burns through the flesh of this eldritch monster. Thick, putrid smoke starts emanating. You decide it is time to run. [ENDING B]
>>>>Option C3: [ITHOTU FLAME required] Burn the vile tunnel monster: You decide to fight evil with evil. As you finish the incantation, the flesh of the tunnel monster starts burning. The lovely song turns into a pained shriek as the flame scorches the flesh of this eldritch monster. Thick, putrid smoke starts emanating. You decide it is time to run. [ENDING B]

ENDING A: Police arrive to gather and identify remains of several missing men. Some of the remains are quite old, meaning that this phenomenon isn't new. A search team is assembled and enters the cave, which turns out to be shallow and empty...
No one knows what truly happened at Mountain 000, but there's no more reports of men dissappearing there.

ENDING B: The shrieks of the dying monster go quieter and quieter as you descend Mountain 000. The smoke coming from the cave should be enough to alert people at Village, but you decide to call the police anyway. The policemen quickly arrive, discovering and identifying remains of many men who went missing in recent months. A search team finds evidence of the bodies being partially eaten, as well as signs of a big fire at the end of the cave. They do not find any signs of the Tunnel Beast... but you know that, due to your actions, it will never again devour anyone.