THe mercenary of the witch

After dying in an accident in which a truck collides with him, Yuto Avis wakes up levitating in a void of endless darkness. Seconds after he floats into nothingness itself, a being opens its eyes around the young Asian. The "Beginning After The End" introduces himself and asks Yuto to help him save an entire multiverse from destruction. Yuto agrees. But... will he be able to defend everyone?