Despite all of this, your rival never outwardly tells you that you're responsible for the death of his Pokémon. He hides his grief and instead channels that energy into the motivation he needed to continue his quest to become Indigo League Champion. The death of his Raticate effectively destroys your rival's impish, childhood innocence. Although he tells himself that he doesn't hold you responsible, he subconsciously holds a great deal of resentment towards you which further fuels his ambitions.
Tearfully swearing upon his Raticate's grave to not fail in what he set out to do, he trains hard in hopes of becoming better than you…defeating you…and to eventually make it to the Pokémon League. Mere moments after he became Indigo League champion, he was defeated…by you. Although he fulfilled his promise to his fallen Pokémon, it was only for a painfully brief instant.
In the end, your rival is scolded by his grandfather while you receive the professor's praise. During the course of the game, you steal your rival's innocence, crush his dreams, and ultimately snatch away the love of his own grandfather. Oh, and by the way, your rival doesn't have any parents. He's an orphan. At that time when I notice at that time, I was shocked and surprised at too because I did know that he had no parents and he was kind of a poor rival and his crushed dreams gave me an example of what he really is when his Raticate passed away, but who knows maybe hes a ghost that cant leave or just an orphan who lost his Raticate in a freak accident and cant stop thinking about it and cant leave his head, digging into his mind and never leaving it until death itself can get rid of it.
But that's how it goes or maybe it's just all in your head.