In an alternate version of Earth, Mika was a genius female swordsman born in 1450s Japan. She spent her entire life training her swordsmanship, pushing her body to its limits, and becoming unrivaled in her skills. When she finally succumbed to her injuries at the ripe age of 45, a System, calling itself the consciousness of the Multiverse, suddenly appeared and reincarnated her into a new world of sci-fi, fantasy, and magic, where flying cars and mythical beings are commonplace and mystical energy known as Mana flows through the air.

Mika's dream is to continue increasing her sword mastery and take advantage of the power of Mana to become even stronger. That seems to be the System's goal, but its intentions are unknown to Mika. All she can do is be thankful that it doesn't make her do anything she doesn't want to do.

The future holds many mysteries as Mika struggles to find her purpose in this new world, but whether her destiny is to save the Multiverse from destruction or to become its executor, she will continue to raise her strength. The secrets of the Multiverse are within reach now, and she intends to make full use of this opportunity she has been granted.

Along the way, she will encounter enemies, new friends and face impossible odds as she fights not just to survive, but to thrive.