Holic

In a world plagued by a new global drug, the world is gradually falling into chaos and death. Companies of the world had devised a new drug that's even stronger than heroin. This drug is known as Spirit Gen, and it's comprised of human souls. Societies on Earth are slowly falling one by one, and leaving nothing behind but death and misery. Until one day, a young boy discovers a vile of Spirit Gen; however, instead of the chemicals corrupting his body, as to oppose to everyone else, it reactions differently and partners with his own soul. This soul he absorbed began talking to the young boy. With the soul, it will aid the boy in future years to come. This dark and mysterious soul's name, is Holic.