As has been pointed out, the basic premise is flawed. He was gifted reincarnation due to the pitiful circumstances of his life. His sister, who caused the pitiful circumstances of his life, is reincarnated as well? Into the same world? And he can be reunited with past acquaintances?
The only way this premise makes sense is if he meant to suffer eternal torment. Another story built on a foundation that is nothing more than a giant plot hole.