Reborn as an Extra

When he opened his eyes he found that he had been reborn as an extra in a novel, which he finished reading yesterday. On top of that, he has become a student of the same battle academy, where the main plot will happen. Let's accompany Rio on his journey and find out where it leads us."i will steal protagonists chances, as for what will happen to main plot if i do so? i don't care!" (Rio)*The book cover doesn't belongs to me if someone wants me to take it down please contact me directly.*(MC is selfish and cares most about himself, rather than following the main story he will follow his own will. and there's no harem too.so, if you like a hero of justice and a plot following type mc with a harem or something then this is not your cup of tea.)