Dr. Kenzo Tenma is a brilliant neurosurgeon whose core belief is that all human lives are equal and that a doctor must save any patient in front of them without moral judgment. Early in his career, Tenma chooses to finish operating on a critically injured boy, Johan Liebert, instead of leaving him to operate on a politically important patient. This decision cost him his status, career, and reputation, but reinforced his commitment to his principles.

Johan Liebert later grew into an extraordinarily dangerous killer and manipulator. Highly intelligent, charismatic, and deeply nihilistic. He is responsible, directly and indirectly, for numerous deaths and immense psychological suffering.

After witnessing the devastation Johan caused, Tenma eventually resolved to kill him to prevent further harm. At the end of the story, Johan is critically wounded, and only Tenma can save him. Tenma must choose between upholding his duty as a doctor to save every life or allowing Johan to die to protect countless future victims.