The ancient city of Pompeii was destroyed and lost to time, but it once housed mighty warriors. High schooler Keidai Saeki is the reincarnation of one such warrior, Sirix, and he carries the memories of that former life.
Keidai doesn't reveal these memories to anyone at school except his closest friend, Mii Serizawa. In her past life before Pompeii's fall, Serizawa was Loleus, Sirix's male best friend. However, unlike Loleus, who had only brotherly feelings for Sirix, Serizawa is in love with Keidai.
Keidai remains oblivious to Serizawa's affection, still longing for Serena—his wife from his previous existence. But his dream of reuniting with her shatters when his new neighbor, Yuuma Ujoh, moves in. Unaware of his own past, Yuuma is actually Serena's reincarnation, and he has developed feelings for Serizawa! Haunted by Sirix's memories and regrets, Keidai must decide whether to cling to the past or embrace a new future.