Keidai Saeki is a high school student with memories of his past life as Sirix Lucretius Fronto, a gladiator in
Pompeii who lost his wife Serena in the eruption of
Mount Vesuvius in 79 AD. In the present, he is reunited with Loleus, Sirix's male best friend who
reincarnated as a girl named Mii Serizawa, and with Serena, who has reincarnated as a male middle school student named Yuuma Ujoh. When Keidai falls into a
coma, he is able to relive the last moments of Pompeii where his actions put Sirix's suffering to rest, allowing him to move on with his life and confess his love to Mii.
Characters ; Keidai is a high school student with memories of his past life as , a Pompeiian gladiator. He is unaware of Mii's feelings toward him and his own feelings for her. As the series progresses, Keidai's feelings for Mii grow as he starts to distance himself from Sirix's memories. ; Yuuma is the reincarnation of Sirix's wife , a maiden who captured the hearts of men with her beauty and kindness. It is revealed that Serena was reborn as a boy because in her final moments, she felt that had she been a man, she could have been at Sirix's side in the final days of Pompeii, rather than be left behind waiting for him. She has a crush on Keidai but remains silent about it, fearing it would ruin their friendship. In her past life, Loleus helped Sirix meet Serena. Kusanagi reveals Mii's name comes from
Serizawa Kamo. Like Keidai, he retains memories of his past life, and hates Keidai for abandoning Serena during the volcanic eruption. He has an aversion to hot weather because of his strong memories of that day. He began working as a student teacher at Keidai's high school after Yuuma's family moved to town. Shinogu despises males except for Yuuma, and is a womanizer. Shinogu holds a grudge against Souichi Mikage because in his past life as Delos, he betrayed Aglaia. Shuna is a kind-hearted young woman willing to help anyone in need. At the age of 10, Shuna meets Souichi Mikage, who also retains his memories of Pompeii, where he served as her bodyguard henceforth. Shuna initially hates Souichi due to his past betrayal, but her feelings for him grow over time and she falls in love with him. ; Reina is Shuna's younger sister who closely resembles Serena and dresses in
gothic Lolita-style clothing. She grew up hearing stories of Pompeii and developed a crush on Souichi. After Reina has her confession rejected by Souichi, she runs away and happens upon Keidai and the others. After framing Aglaia for murder, Delos sought revenge against the House of Britius and murdered every member of the family. ==Publication and conception==