Deciding they need a bit of a break, Koutarou takes the girls out for a day of beetle hunting. An unexpected reunion, however, leads Kiriha to realize there’s more than just beetles in the mountains outside of Kisshouharukaze City. It seems the radical faction has been working in the shadows all this time, and they’ve already established a foothold on the surface. But a factory? Magicians? Automated weapons? It sounds like they’re preparing for something big, but this is only the beginning.

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!

Koutarou and the girls prepare to chase Ralgwin back to Forthorthe, but one critical mission remains before they can leave Earth behind again—they must oversee the welcome ceremony for the next wave of intergalactic transfer students. Little do they know that someone is watching their every move from the shadows, someone with a keen interest in both Koutarou’s sword and Nalfa... Indeed, the Gray Knight is getting dangerously close the group and the truth about what happened back in the ruins. Will their rematch with him be their final showdown?

In this special collection of stories, new and old friends alike appear. Shizuka tells the story of how she lost her parents. She also comes to learn of the very special power that's been sleeping within her, and just what consequences that has for her... waistline? Yurika goes on a little quest to try and find herself, or rather, herselves. And finally, the story of how Koutarou knows Theia's mother.

Now that the invaders have come to an understanding of sorts, things are going smoother than ever in room 106. Spring is in the air--tulips, friendships, and potential romances are all about to burst into full bloom. Koutarou and the invading girls have never been happier together, but nothing lasts forever. Things turn dark quickly when they find out that they're going to have to say goodbye to one of their own... and soon. Without even any time to prepare, will the bonds they all share be enough to pull them through?

Koutarou has sunk into despair. He was given the agonizing choice of saving either Fasta or Ralgwin, with the other losing their life. As a result, Maxfern was resurrected, leaving Koutarou at a loss and full of fears. What will be the catalyst for his recovery? The girls of room 106 struggle to reach out to him, but it’s an unexpected friend who pulls Koutarou back from the edge. Once out of his slump, he resolves to take action against Maxfern. In order to find any leads on their enemy, Koutarou, along with Maki and Nana, infiltrates an enemy organization!

 Yurika has made the bold decision to attack Darkness Rainbow’s base in order to try and prevent all-out war in Folsaria. It’s going to mean a bit of a field trip for everyone, and a very big battle. Koutarou and the girls will have to consolidate all of the power they have—and maybe borrow some help from a few new(?) allies—to get home safely this time. There’s a strange enemy on the horizon, but perhaps the only thing harder than fighting yourself is fighting someone you love...