Black Bullet
Delicate balance
Rentaro was infected with the gastrea virus as a child. Suppressing it with his will to live, he had a surgery to implant high quality vibranium in him as a right leg, right arm, and left eye. The vibranium suppresses the virus in him, but slowly kills him, lending him a delicate balance that is tipped only by his desire to remain human with Enju. Rentaro must inject himself with the virus during the second fight with Hiruko Kagetane at the harbor to remain alive, leading to the balance being dipped into cursed child territory and causing Rentaro to require the same medication as Enju to keep the virus at bay. He does this in secret to keep Enju from worrying about losing him.
