I recommend to you "Transformed Manga Ji" and "Transformed Nine-Tailed Fox Fairy that Traversed the Other World". Among them,"Transformed Manga Ji" told the story of a protagonist who could transform into various anime characters to save the world, while "Transformed Nine-Tailed Fox Fairy" was the story of an otaku who transmigrated into a nine-tailed fox otaku and became a strong person with the help of the system. I hope you like my recommendation. Muah ~