Buso Renkin: Vol. 1

This anime series follows teen Kazuki Muto, who attempts to save -- and is later brought back to life by -- Tokiko Tsumura, a pretty damsel under attack from a beast known as a homunculus. But as it happens, she's part of an organization sworn to safeguard humanity from the homunculi, and after she implants Kazuki with a device that gives him the power to fight them, he and Tokiko join forces to vanquish the evil figure controlling the creatures.