Mephisto Bart Kucabara is a devil lawyer. To return to the demon world from which he was exiled, he must collect sufficient Dark Matter. His strategy involves claiming Dark Matter from the souls of sinners condemned to hell; if he proves a soul's innocence, the Dark Matter becomes his. However, how can he accumulate enough Dark Matter when his kind nature leads him to constantly expend it defending souls against the Shinigami who have come to take them to hell?