Seiken Tsukai no World Break or WaruBure (World Break - Aria of Curse for a Holy Swordsman in english) is a Japanese light novel series written by Akamitsu Awamura and illustrated by Refeia.
The series takes place in a private high school involving the concept of “saviors.” They are known as people who possess awakened memories of their past lives. The story tells of a young boy named Haimura Moroha who comes to this private school.
At the school, there are two types of people: White Iron, who fight enemies with weapons and techniques gleaned from the Prana powered from their own bodies, and Black Mages, who wipe out enemies with magic to manipulate the Mana powers that surpass physics. Moroha is the first person with past lives of both White Iron and Black Mage.
Power of the Verse
The most common Saviors are between Wall level and Building level with Subsonic speeds. S-Rank Saviors are powerful beings who are considered unique and "monsters", which are at least Small City level with Hypersonic speeds.