One day, the 30-year-old office worker, Koutarou Matsunaga, is stabbed by a thug while protecting Seina Isezaki, a high school girl who lives nearby. And just as Matsunaga's life is about to end, he is revived from near-fatal wounds by Seina's power. But his relief is short-lived, as Matsunaga's newly awakened power suddenly goes out of control, and the two are transferred to another world. One of swords and magic, where Seina once lived as a Great Saintess.

However, Seina, who was once reliable, can no longer produce magic power, and can only manifest holy magic through Matsunaga's supply of mana. As they continue on, Seina's feelings for Matsunaga, which she had kept hidden, escalate more and more...!? Eventually, Matsunaga awakens to time-space magic, allowing him to freely transfer between Earth and the other world. At that moment, Matsunaga thought to himself.

"I can live without being an office worker anymore, right?"