All the OCs are from of an orphanage in Takigakure, they are spies for Tsukikage Kuragari.

Amabie (female) once her teeth grew in and were shark teeth (which neither had) dumped her at the front of the orphanage. She's embarrassed of them and she likes going to local farms to help. She is named after a mermaid japanese yokai

Shigeru (male) was born with amelia that made him not to have a left forearm, which he was also dumped in front of the orphanage. He is named after Shingeru Mizuki, the author of GeGeGe no Kitarō(relates to folklore), he also lost his left arm in WWI

There is another male who lost his parents in a fire, and so he was placed in the orphanage. Not sure of his name but his hobby includes kite flying and he has a phobia of big fires (for cooking he's fine, but fireplaces wouldn't be).

The orphanage's founder was killed after refusing someone who wanted to use the orphans for child trafficking for money. Not sure of the names of both of them yet (both will be males)

Because of the refusal, the person who wanted to use the children ordered ninja to kill the orphanage founder.

Still working on more details but basically the three escaped the orphanage and became ninja in order to stop the child trafficking and they heard about Tsukikage Kuragari, so they joined them for spies in hopes to gather more information