Makoto lived in Kyoto nearly his whole life with his mother and father, enjoying life to the fullest until he was diagnosed with COPD(Chronic Obstructive Pulmonary Disease) at age 15, and he was forced to leave all of his friends to live in the small village of Chibu, Shimane. His doctor recommended this action to his parents to live outside cities to help increase the time he has left, but a diagonsis on his 19th birthday, which shocked his doctor, showed that living past age 21 will be impossible for him and recommended an upcoming MMO called Sword Art Online for him to try enjoying life as much as he could before the end.
Makoto created a character named Viper for humor's sake and enjoyed the virtual environment of Aincrad, he initially thought that if he was going to die, atleast he wants to die in a beautiful world like this.
However, once Kayaba announced that he changed SAO to a death game, he lost his mind; the perfect paradise he experienced has become the underworld of death and despair. Viper decided that he doesn't want to wait for his death to come. He plans to become a PKer to provoke a response from powerful players that would want to end his life in combat, the way he wants it to be.
In the meantime, Viper's doing what he can to prevent other PKers from 'taking his targets' as he claims, and during his campaigns, he often 'accidently' lets his targets escape, but quickly flees before authority like the ALF arrive, hoping to build a reputation of a player looking for a specific person to fight.
Makoto has always been easily misunderstood in his intentions, most people see him as a delinquent because of his appearance but he is always thinking of the greater good. He wants to prevent the PKers from killing as many people as he can, while looking for his dream opponent, so he doesn't need to worry about dying in vain.
Viper's character song is Light my fire , he symbolizes this song in the sense of him wanting to make his future demise meaningful, also, no matter what, Aincrad is his permanent home.