Review Detail of Irithos in Modern Weapon Summoning System

The story started out fine, but then about halfway in they leave the medieval setting and travel to WW2, which was a radical difference from the beginning. Eventually most of the chapters are just repeats. And then some weird stuff about their parents and dying and the story goes silent, and all the chapters named [updated later] and not updated. Also during that halfway plot the whole revenge against his team who betrayed him just dissapears. I don't find it makes sense to go with a WW2 setting halfway through.