This is a Mary Sue story.
A 15-year-old Mary Sue transmigrates into the world of Hunter x Hunter as Yoshihiro Togashi's bodyguard.
...Actually, one god was angered by Togashi's hiatuses, so the god punished him by sending him into his own work to go on adventures. A Mary Sue was assigned to protect her, and he was also given a notebook: anything written in it would come true... except death.
Please don't flame this Mary Sue story.