Help finding the title

[otaku051502]

I'm looking for a manga about a Grim reaper apprentice and a mysterious girl

In the world corpses rise from the dead and special grim reaper are the only ones that can make them rest in peace or using special tools

Spoiler: About the plot

So the story start with the grim reaper apprentice and his class on a train for their final exam then they are attack derailing the train now he found a mysterious girl and later he got accused of attacking and killing his fellow apprentice there's also a special metal that has a property that can stop corpses from turning and attack people