A boy who accidentally traveled through time in a book became a non-human being.
He also recognized a god-sister, but he didn't know that his god-sister = the protagonist's mother until the god-sister's son was born.
From then on, he lived a life of hugging the protagonist's thigh and avenging his sister.
However, later on, the protagonist's attitude towards him became increasingly wrong? !
Since I am a newbie writing, please forgive me if there are any bugs or wrong characters.