With the end of the year approaching, things are getting busy around Corona House. Even though it's winter vacation, there's a new play to get ready for, Koutarou has picked up a new part-time job that no one seems to know anything about, and Ruth has decided to take up martial arts training. Come January, preparations for "The Silver Princess and the Blue Knight, Part 2" kick into high gear, but when an old rival reappears dead set on revenge, Koutarou may be in for the trip of a lifetime.

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!

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?

Now that Koutarou and company are back from their long journey to Forthorthe, everyone is hoping to settle back down into their normal, peaceful lives. Things are quickly thrown off course, however, when Theia, Ruth, and Clan show up with a little extra baggage and Koutarou suddenly finds himself in the midst of intergalactic negotiations. Has the real alien invasion just now begun? And what’s with the strange voice Sanae keeps hearing? Moreover, what’s got Clan so pensive?

Back from his unexpected travels, Koutarou tries to settle into his life as a normal high school student again. A school field trip to a ski resort sounds like just the right thing to do the trick. When they get there, however, Yurika notices that Maki is sneaking into the mountains to use magic. Worried that Darkness Rainbow is up to something, Yurika goes to investigate, but the investigation turns into a lot more than she bargained for when she comes across a demon.

Valentine's Day is right around the corner, and the girls of room 106 are scrambling in preparation for it. It's not all fun and games, however, because not everyone seems to be able to admit their true feelings. Ruth receives a strange message from her parents back home in Forthorthe, leaving her with an important decision to make about her future. And on top of everything else, she seems to be getting closer and closer to figuring out what happened to Koutarou while he was away.

Koutarou and Clan are working their way back home from their interstellar adventure, but they have to make a pit stop about ten years off from their intended destination. As luck would have it, they encounter a young girl right after they land. Worried that she might have seen their spaceship in action, Koutarou decides to dig a little deeper. Things take an unexpected and heart-wrenching turn, however, when he realizes he has more in common with this girl than he initially thought.