Ability: Reflecting sound
Threat level: Low
Human friendship level: Extremely High
Main place of activity: Youkai Mountain, Myouren Temple

If you shout in the direction of a mountain, youkai known as yamabiko will give a sincere reply. They are youkai that were extremely common since long ago, and could be found on every mountain.

They are bright and cheerful youkai that will respond to happy voices with a cheerful one of their own and return an equally angry retort at mad shouts, but in recent years it seems their population has been declining.

The reason for this is a rumor started among the humans of the village that the truth behind the voices of the yamabiko are just the reflections of sound, so many humans haven't been shouting in the mountains recently. Many yamabiko lost their purpose in life, and so have been naturally continuing towards extinction.

Thinking that such a world was empty, she entered the priesthood. Right now she is apparently training at the Myouren Temple. She says that her training involves cleaning the main gate every day. She has apparently memorized most of the sutras from hearing them from inside the temple(*1). Of course, she doesn't know what they mean.

As can be surmised by looking at her big ears and small tail, she was originally an animal youkai. However, she does not possess any savage habits as meat-eating beasts normally have. Despite her speaking in a loud voice, she is comparatively timid, and when she runs into guests that are climbing the mountain, she disappears quickly. After that, she'll call out in a loud voice from a distance "Did that surprise you?". Shouting from far away probably means she's basically shy.

As a side note, when she's alone she is supposedly a well-behaved youkai, but lately she's started to mumble sutras to herself. She might be have a lot of stress.

1: The youkai before the gate, reading an unlearnable sutra.

A yamabiko replies when you shout out from a mountaintop. While the standard is to reply with the same words, there are special cases in which the reply you get back is different. I've documented them to the best of my knowledge.

"Yaho~!" -> "Yafu~!"
The basic form, they're too used to it so the pronunciation is sloppy.

"You idiot~!" -> "What did you just call me?!"
The adolescent form, also called the delinquent form.

"My apologies!" -> "No, that was my fault!"
Adults have proper manners.

Yama~!" -> "Kawa~!"
This is limited to Mr. Yamakawa.

"What time is it~!" -> "Well, it's about~!"
The wristwatch form, they know the approximate time.

"One plus one is~?" -> "..."
The bad at math form.

Unless you attack her yourself, there's no particular danger. She's a youkai with an especially gentle personality. It should be fine to head to the mountains on a nice day, raise your voice and enjoy yourself.

But please don't bother the Myouren Temple by raising your voice there, even if she's been staying there lately.

On the other hand, if you're too noisy you may end up attracting other mountain youkai, so be moderate.