Human Lost: Ningen Shikkaku

The year is 2036. A revolution in medical treatment has conquered death by means of internal nanomachines and the “Shell System”, yet only the richest can afford to partake.

Yozo Oba isn't the richest. Troubled by strange dreams, he flippantly joins his friend's biker gang on an ill-fated incursion to “The Inside”, where society's elite lives. This instigates a journey of terrifying discovery that will change Yozo's life forever.

(Source: Funimation)