A girl named Rachel tells a boy named Bam to forget about her as she is climbing the tower to see the stars, disappearing into the gates. Bam suddenly finds himself within the first floor of the tower, with its caretaker Headon. Headon explains that all who wish to climb the tower must pass through a series of tests from each floor, with the first being to reach and break a ball behind a giant white steel-covered eel. Before he can enter the cage, however, a girl named Yuri and her companion Evan interrupts him, gifting him a Pocket holding information about the tower that can switch between visible and invisible, as well as allowing participants to understand the tower's language...