Medaka Box (2012)

S2E5 You Can't Be Killed!

Title: Invincible Threat! Plot: With every motive justifying murder, Munakata Kei becomes an unstoppable force. Medaka finds herself unable to confront this lethal adversary, leaving her best friend to step up and face the danger. It's a race against time as she must summon all her courage to protect Medaka from a relentless killer.