Notes

Horse: A man, almost a wind spirit, who traveled the four corners of the world and was fiercely independent. When he was chained and taken to be sacrificed, he refused and used the forbidden spell of reincarnation (that he heard from the whispers in the wind) on the sealed away monster underneath the summoning alter to unleash mayhem so they'll both be free.
Reincarnated, the reincarnator was a test subject in a facility for most of their early life. One day, a tall, cold man dressed in black came to save them, and endeavored to show them the world.

Sheep: There was a poor village girl who didn't have much time left in her life. One day, while by the river, she met a mermaid and they became friends. She hid her illness from her, and enjoyed being treated as a normal person. However, when she was nearing the end of her life, she regretfully told her that she couldn't see her anymore. The mermaid, having noticed the signs but haven't said anything, offered to give her heart and blood so she could heal. Hesitant, the girl accepted, but used the reincarnation spell not long afterwards.