I actually do not like your character
First is the weapon of choice, the cutlass seems really uninspired and the fact that his fighting style "is more effective against other magi than against wraiths" is astonishingly illogical since, as a magic boy, you are supposed to kill wraiths, not other magi. The magic seems boring and generic, not to mention completely unrelated to his wish and personality.

Second is the back story, which wasn't even supposed to be there. A bit of drama is okay, but you are clearly forcing it to ridicule levels and he was supposed to be freaking less than 11 when all of this misfortune happened to him, all in all not explaining actual important things like how come he wasn't in an orphanage (Tokyo is not precisely a third world village) or how did he even get into a school or education. He has been fighting since he was 11, when did he have time to go to school? Of course, he didn't go to school, but then he acts magnificent and highly as a cynical. Who took care of him? Alone his whole life? How about when he was a baby? It doesn't make sense. The time he killed his friend clearly was a despair horizon and he should have transformed into a wraith there. 

The personality, which wan't needed either because you are better showing than telling, is constantly shouting at me "why". Everything indicates that Souta is already in complete despair. What kind of hope a person like that has? He has no friends, suffers horribly emotionally. It is contradictory that he is unable to trust or believe anything and then you say that cares about others. He acts like the toughest guy in the world and we are supposed to believe that because of the back story when is only 15 years old. A 15 years old teenager has been fighting to dead four years, hates the world, lives in constant anger and is completely alone. That screams despair to me

Overall, I thinks this is very badly written. A character that was thrown as many bad things as possible regardless of how impossible they are in order to excuse a cringe worthy personality spawned as a dark mary sue that has no real weakness (being distrustful, having angst and being edgy with a dark troublesome past are not weak points) coupled with vague abilities that are specifically described to be in advantage against the rest of the players ("best at fighting other magi") makes me think that you need to reconsider 

however, I'm not the one that ultimately chooses, but still I'm telling this so that you improve