Seraph of the End (2015)

S1E3 The Demon in Your Heart

Y?ichir? discovers that a fellow student has fallen under the influence of a demon and resolves to confront him. His aim is twofold: to rescue his classmate and to forge a pact with the demon for its power. However, Y?ichir? quickly realizes that taming the demon is far more challenging than he anticipated, leading him into a battle of wills that tests his strength and determination.