A Friend from the Past (haikyuu creature au)

"The letter is written from someone I don't know."
"Who could it be?"
"Hey don't look at me, I don't know either."
"I think it's time we visit our old friends."

Somewhere else:
"SHE'S BACK?!"
"BOKE HINATA BOKE!"

"SHE'S BACK?!"
"KIYOKO-SAN!"

"SHE'S BACK?!"
"WHAT THE HELL SHITTYKAWA?!"

"SHE'S BACK?!"
"Are you okay, Tendou?"

"SHE'S BACK?!"
"Calm down Bokuto-san."

"She's back?!"
"KYANMA, ARE YOU OKAY?!"

"She's back?!"
"SUNA, WAKE UP!!!"

"She's back?!"
"HE TALKED?!"

"She's back?!"
"Huh? Who's back?"

Once upon a time in a world of magic. Humans and Creatures lived side by side. Let's just say these two have the worst relationship, their like cats and snakes, or plants and eagles... Or something like that.

Well... back to the story, a war started between the two races, which ended with the disappearance of the Creatures.

Centuries passed and humans grew and have forgotten about all types of creatures. They only appear in children's stories as monsters or even villains. Humans have thrived and will never accept anything peculiar, so every creature that they found was killed in cold blood.

Until one day, someone has the brilliant idea of using these creatures as weapons. With that, the government took the liberty of many young and naive creatures. They experiment and brainwash them into being their perfect little weapon.

This is just the case for Shoyo, Kiyoko, Tooru, Satori, Kōutarō, Kenma, Rintaro, Takanobu, and Kiyoomi. They are experimented and hurt, that was until someone broke into the facility and saved them.

What happened if the person that saved them got a mysterious letter telling her, the children that she once saved are being hunted down and going used as weapons?

Will she come back to save them, or will she ignore the mysterious letter? Will she be able to resolve everything or will she find something impossible to solve?
Read to find out what happened...