Bubble

In Tokyo, after bubbles that broke the laws of gravity rained down upon the world, the city has become a playground for a group of young people who have lost their families, acting as a battlefield for parkour team battles as they leap from building to building. Hibiki, a young ace known for his dangerous play style, makes a reckless move one day and plummets into the gravity-bending sea. His life is saved by Uta, a girl with mysterious powers. The pair then hear a unique sound audible only to them.

Synopsis from Anime News Network