Summary of the plot
Reiji is a typical student on the remote southwest island of Tsukuyomi-jima. However, due to an unexpected event where his life was in danger, he awakened as the 13th magical summoner. After summoning the spirit and magical superweapon Sakura, she gifts him with the special ability ‘Da Capo,’ which allows him to summon anyone who he met in the past 24 hours or reverts items back to its previous state (up to 24 hours ago). Now they must participate in a battle they cannot avoid.
Power of this verse
A lot of Hax abilities make this verse extremely strong. Some characters like Sakura, Ryuichi, and Umi have the power to destroy the world right in the beginning of the series. The top tiers can manipulate concepts of time, space, have limited-probability manipulation, etc...
The series has later shown that it has a multiverse, but as of yet, no character has ever shown power beyond universal scale.