Kami no Tou: Tower of God

A tower selects individuals known as "Regulars" and offers them the chance to fulfill their greatest wishes, such as power, wealth, or recognition. A boy named Bam has lived in a dark cave with only a tattered cloth and a distant light for company. When Rachel appears through that light, she introduces him to the outside world. As their friendship grows, Bam learns about life beyond the cave. When Rachel decides to leave to enter the tower, Bam is devastated. Determined to find her, he approaches the tower and unexpectedly gains access. Unlike the Regulars, Bam is an "Irregular," someone who enters the tower without being chosen. His arrival disrupts the tower’s established order.