Invaders of the Rokujouma!? Volume 3

Summer vacation is right around the corner, but can Koutarou and the invaders manage a ceasefire long enough to actually enjoy it? Luck seems to be on their side when Ruth wins them a trip to a seaside hot spring, but it's not all fun and games with shadowy figures stalking their every move. When push comes to shove, can rivals become allies to save one of their own? Or is it every invader for themselves?