Yakushi Tadashi believed no one should spend their last moments alone. Yet, when a devastating virus ravaged the world and quarantined majority of the infected, he died alone with the wish to have someone by his side.

To his surprise, his wish was answered in the oddest way when he's reborn into another world — as a blade! Not only that but the stalwart companion of the realm's hero, Kozue. Forty years pass, and the tales of Kozue's deeds intermingle with awe and desire of her legendary blade. However, no one could convince him to leave her side.

That is until Kozue introduced a girl named Yua as a candidate for his new companion. Whether she was worthy stood to be seen but with the designs various parties have set upon her, if he did not protect her, she may face a fate worse than death before she has a chance to try.