Killer rengoku

You were on your way to your new mission. A boy should be waiting for you nearby. You heard rumors about him: a few years ago, his entire family was murdered by a demon. And a few minutes later, you spotted him leaning against a wall. You waved at him, only to be met with a cold gaze. As you approached him, he looked at you 'Let's go.' His icy tone sent chills down your spine