In Kaiba's universe, memories can be stored as information via a memory chip; when individuals die, their minds live on. This digitization of mental information allows for the transfer of one's mind to someone else's body, and the theft and manipulation of other people's memories has become the norm. Society is largely divided into two classes. In the skies are electrical storms, which cannot be passed through without losing one's memories. Above them lies the realm of the wealthy and powerful, who barter others' bodies and memories for their own enjoyment and longevity. Below the clouds is a troubled and dangerous world where good bodies are hard to come by and real money is scarce.
The series begins with a man named Kaiba as he awakens in a ruined room. He has no memories, but he has a hole in his chest, a triangular mark on his stomach, and a pendant with a picture of an unknown girl inside. After being attacked, Kaiba escapes and, through his travels, regains his memories. Meanwhile, the woman from the pendant struggles with her own convictions and her past, which may be intertwined with Kaiba's origins.
