OK, I remember this novel about a person with a system that helps the user upgrade or evolve his pets but it is during modern time and he is the only person with a system and the rest of the world animals is normal afar I can remember. he is also a reincarnated person if I remember correctly. I also remember he bought a snake and a mantis which he also use to kill people with. another thing I remember is that he applied to be an assassin or something and his first kill was with a bee that killed this Gansta boss or mafia person.