In the ancient city of Pompeii, powerful warriors once thrived, but the city was eventually buried and forgotten. Keidai Saeki, a high school student, is the reincarnation of one of these warriors, Sirix, and retains memories from his former life.
Keidai keeps these memories hidden from everyone at school, sharing them only with his best friend, Mii Serizawa. In her previous incarnation, Serizawa was Loleus, Sirix's close male companion. While Loleus had only platonic feelings for Sirix, Serizawa now harbors romantic feelings for Keidai.
Unaware of Serizawa's affection, Keidai continues to pine for Serena, his wife from his past life. His hopes of reuniting with her are dashed when his new neighbor, Yuuma Ujoh, moves in. Yuuma, unaware of his own history, is actually the reincarnation of Serena and has developed feelings for Serizawa. Torn between the past and the future, Keidai must confront his memories and decide how to move forward.