Things have finally quieted down for Koutarou and the Corona House crew, meaning it’s time to kick back and have a little summer fun! Things start off at the beach where swimming, volleyball, and a test of courage are all on the menu. After that, there’s still plenty more fun to be had at a local festival and the amusement park. But when summer vacation draws to a close, Yurika’s worst nightmares come true... And what’s this about a surprise visitor at the apartment?

After getting back from Forthorthe, everyone was hoping they could spend their days in peace for a change. But as if the politics of the official Forthorthian invasion weren’t enough, something very strange and very unsettling is starting to happen around Koutarou and the girls. One mysterious disappearance becomes two, and there’s no clear cause or end in sight. Can they figure out what’s going on in time, or will Koutarou end up just like he was in the beginning—alone?

Just starting high school, Koutarou is moving out on his own to take some of the burden off of his widower father. Lucky for him, he's found a room at Corona House. It has a great landlord, it's not too far from school, and best of all, it's dirt cheap. It really is perfect... except for the strange girls that keep appearing to try and take it over! But even as room 106 turns into a battlefield, Koutarou isn't willing to give up his apartment without a good fight. The invasion begins!

With things coming to a head between the radical and conservative factions, it’s time for Kiriha and the others to take a stance. After discovering a cataclysmic weapon in the hands of the radicals that stands to threaten both the surface and the underground, can they act in time to prevent tragedy? The clock is ticking, but it won’t be the only thing working against them since the radical faction has a little... outside help... on their side.

After Theia receives a distressing message about her mother in Forthorthe, she's forced to make what could be a life-changing choice. Nothing is simple, however, when it comes to the politics of a galactic empire.

Harumi has a special favor to ask Yurika concerning Koutarou, but Yurika will have her own set of relationship problems when a new transfer student shows up at school the next day. The new girl--Aika Maki--is an acquaintance of hers, but she's not the old cosplay friend everyone seems to think she is. If what Yurika says is true, Maki is the evil magical girl that she's been trying to warn the others about all along. The biggest danger now may be that no one believes her.

With one of their own in trouble, Koutarou and the others are left reeling. Clan thinks she may have gotten to the bottom of things, but if what she says is true, the crisis they now face has been in the making for thousands of years. But the surprises are far from over there. A strange message for Koutarou could mean a tentative new alliance with a most unexpected partner. The offer comes at a time when they could desperately use the help, but what will the true cost be?