Spiritual Successor

Over 30 years ago, the world was nearly destroyed in a horrible catastrophe. However, a spiritual force saved it without Humanity's notice, restoring it anew with things once believed to be fantasy. Now, with the world at risk once again, it is time for a successor to wear this mantle. (Spoilers for Volume 18 and up) [Shido/Harem, with Mio as the Main Girl]