Subarashiki Kono Sekai The Animation

A character named Neku wakes up in the middle of a crowded street crossing in Shibuya with no memory of how he arrived. He soon learns he has been moved to a different realm called the Underground. Forced to take part in a dangerous game called the Reapers' Game, he teams up with a girl named Shiki. They work together to complete tasks and fight creatures known as Noise. As they progress, they slowly learn more about the nature of the game. Survival depends on trusting one's partner.