Zuri lost her mother not long ago and while in the midst of facing her grief, she finds a strange sword. Vesper, a sword spirit, wakes to Zuri after thousands of years of slumber and requests Zuri to be his Master. In return, Vesper promises to help Zuri find the murderer of her mother and get revenge.

The Nematocera Emperor has been quiet after a recent war, The Mosquito war. However, the said heir to the throne, Prince Toshaki, will hopefully become the new emperor and set a peaceful future with the Konchu Empire. But will he really? Ryusaki, the leader of the Mosquito Slayers must found out if Toshaki is really going to work together for a better future.