Spirit Circle follows Kouki Fuuta, a high school boy who gains the ability to see spirit circles, which float over people's heads and reveal their past lives. After a mysterious transfer student named Isuzu attacks him, Kouki discovers that he and Isuzu have been locked in a cycle of reincarnation for centuries, each life ending with him killing her. As he remembers their shared pasts across different eras—from ancient civilizations to futuristic worlds—he uncovers the tragic origin of their conflict and seeks to break the cycle. Readers enjoy it for its unique blend of action and philosophy, the emotional depth of the past-life reveals, and the way it explores themes of karma, redemption, and the enduring power of relationships.