Akuma-kun

The age of demons has arrived. Dr. Faust, who predicted this surge of evil, is nearing death and can't fight it himself. Instead, he passes the duty to a boy named Shingo Yamada, tasking him with purging the Earth of this new darkness. Faust spots a birthmark on Shingo's forehead-proof he’s the chosen warrior against demons. To aid him, Faust summons Mephisto, a reluctant devil from hell, who might be humanity's last hope. After sealing their pact in blood to protect mankind, Shingo and Mephisto set off to face the supernatural.