Katsumi Yu embarked on a philanthropic mission as a physician to Africa three years ago. However, his plans were soon quashed when a rebel uprising broke out, and he was taken captive by the guerrilla group. Despite the circumstances, he continued to render medical aid to the ailing populace, and this continued for subsequent years. But the tide changed as the oppressive regime was replaced, and the guerrilla movement was set upon. Yu found himself in a dire situation where he had to choose between taking lives or losing his own. He opted to quit his medical practice and marked himself with a Luciferian tattoo symbolizing his past misdemeanors.
Upon returning to Japan, Yu fell into a life of debauchery, spending his days drinking his sorrows away. Following a drunken brawl, he woke up in a questionable medical center owned and operated by Dr. Minatono, who treated all patients, even those without insurance or resources, using the most advanced equipment. As it turned out, Dr. Minatono catered to individuals, including the mob, who could not access conventional hospitals due to legal constraints, and in return, charged hefty fees to sustain the facility. Yu initially declined the job proposal, but a series of events transpired that kept him occupied in the operating room.
