You shouldn't say that something's impossible unless you understand what it is and why it can't be. You say the Bone Eater's well cannot be replicated because it is impossible, but how did it happen in the first place? And claiming that there's only one Shikon jewel, do you understand what it's made of, that it is so unique?
You don't?
Are you sure?
Well, if you ever do, call me. Tell me. I would really like to be told that it's impossible in such a way that I can believe it. If only to get some sleep.

detail one reason why the Youkai Community maintains separation from the human race, and write down three ways it does so.

Hmm... Sumire bit down on the end of her pencil in concentration. A fly could be heard buzzing in the classroom. Then a loud slap came as the teacher flattened it against his desk with the palm of his hand. Behind her a sigh could be heard - a vile boy named Mushi was sitting there, and he was impartial to insects. A dumb way to cheat. Sumire shrugged and began to write.

"Since the industrial revolution the human world has developed formidable weaponry, and is capable of seriosly harming the youkai population. Also, the human's thirst for knowledge might lead to the turning of youkai into test subjects in order to measure and harness their magic."

She looked up and saw the teacher. Hiromi-sensei was staring at the class intently, aware of every breath and motion. With such immobility he'd pass for a marble statue even if he wasnt the color of granite. Also, he was a fundamentalist, and even if that answer was correct, he'd fail her for portraying humanity as strong... Or not weak for that matter.
Sumire cherished the truth, and really liked to tick off Hiromi-sensei (he usually went maroon and started stuttering when angry). But the cost could be her diploma. No diploma- no permit to leave premises alone. Being stuck in Momachi forever, the only source of entertainment the progressing craziness of her big brother. And the icing on the cake- an arranged wedding. So screw the truth.
Sumire crushed the paper and on a clear one wrote down-

"Humans are envious and greedy, and as such will not let go of the youkai magic. Thus, as long as demon sanctuaries are scattered between populated human cities, the secret of the youkai must be kept, as the war that will be started by humans upon discovery will be long and bloody for both sides."

There, that's better.

"Guard keep charms are as follows:
1. A human that enters the town will die by sundown unless treated to food and drink by one of the youkai who belong to the town. The protection will work for one day, the next day he'll need to be offered food again. If fed for seven consecutive days, the human may remain in the city, but if he/she leaves it they will die. Exception- humans with priestly (magic) powers, which are uncommon.
2. A non-graduate youkai will not be able to leave the sanctuary alone. If leaving with a companion he must remain within companion's sight, or he will lose conciousness and eventually perish. No exceptions.
3. All youkai passing through the gates will be stripped of his demonic appearance and assume a human one until return. Exception- unborn. "

After a thought Sumire erased the last sentence- pregnant demonesses cannot pass the gate, for fear of being evacuated to a human hospital to push out something with talons or fangs- something that's generally more of a cub than a baby. Youkai are proud to settle for whatever poor grade of medical assistance the local infirmary offers. The doctors there are even more proud to settle for little more than medieval tools. She scoffed, setting her paper at the desk, and walked out of the classroom.

A tall girl was leaning on the brick wall next to the door, she greeted her with a smile.

-Ugh, you take like, forever.- She complained, touching an elegant finger to her crown of antlers.

-Sorry, Chio.- Sumire smiled. -This is the last one, last chance to improve it.

-I hope you don't blow it.- Chio-chio smiled crookedly.- Wish they could grade you on all that extra stuff.

-Yeah right. Lemme just walk over to old Hiromi and ask him if he'd grade me on computer science.- Sumire scoffed. - He will explode. Anyway, I hope I passed this one.

-It's just one, don't worry 'bout it.- Chio shrugged.

-Yeah... -Sumire sighed. -I aced Advanced Illusion, I know I did. Herbs too. Really fucked up Healing though. And Spells yesterday- I'll barely pass, if at all.

-Chill out.- Chio said definately.- It's not like you're staying here... You only need to pass, right?

-Um, yeah...- The girl trailed off.

The two walked for a while in silence. Sumire just dragged herself after her older friend as she walked towards a small cofeeshop. Chio could afford it- she had passed all of her exams, and left town for Tokio half a year ago. She was the fifth daughter in a big family, and her parents just quietly disowned her, as opposed to hunting her down . Sumire's brother only had her, so she wouldn't be so lucky. If she ever left, she'd need to settle quickly and never look back.

-Hello? Solar system to Sumire?- Suddenly she noticed Chio was talking to her.

-What?

-I asked, what's your groom like? Hot at least?

Sumire flinched. The groom was the reason she had to rush out in the first place. Her brother and her were the only remnants of a once- important youkai family and her brother was hellbent on restoring the old honors, by marrying her to someone rich. Rather then finding himself a girlfriend to keep busy.

-Yes, somewhat.- Sumire agreed objectively. -But sleazy... I dunno. You know, he's Egao. Word on the street is that sons of Egao...

-Bathe in bleach, yeah.- Chio snorted. -Maybe they just can't read warning labels. Did he like you?

-He's... Very keen. -Sumire looked down. -You'll get me out of here, right? Because if you don't...

-I'll get you out of here. -Chio smiled, reassuring. - You trust me. I will.