D15, or as he addresses himself 'Dis' is dead..in fact, he doesn't even remember being alive. Don't feel bad for him. That's the same for all of the reapers. They work under a narcissistic and intimidating man called life and are paid in memories for their services. The more they remember the more like their old self they become in appearance and attitude. Oh yeah, and here's the kicker. If you go too long without regaining memories... you'll die.