looking for a manhwa

I'm looking for an action manwha I forgot the title of it here's what Ican remember from the plot:
the MC was summoned to another world as dark mage/hero by their saintess but was as "prize" for saving the world he was granted to return to Earth. Now upon coming back the earth is invaded by monsters and he was recuited to be a soldier for Korean Army and he enjoys the training because it was easy compared to what he got from the other world. One of his fanatics was able to come to earth then started investigating about the unusual appearance of otherworld monsters (from the reader's perspective the culprit was the saintess from the other world who kept sending monsters down to earth).

please help me find this manwa. Thank you.