Again, just my personal opinion. If you're fine with it, then by all means, let it pass. I just personally find that being neglected by one's rich parents, watching your best friend die before your eyes, being avoided shunned by everyone because of accidents as a still young child, and possibly the scars and missing eye depending on their cause (it wasn't specified how he got them), is a little too much for a series like Soul Eater NOT. I mean, if we're being closer to the original series, we do have characters like Crona, who was horribly abused by Medusa and had to put up with Ragnarok, but yeah...That, and the personality which is similar to other edgy characters.
Again, it's my opinion, and if you think it's fine, well, you are the GM, and ultimately, your opinion is what matters. :3