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...

Volume 20 is a special collection of side stories. First up, Yurika announces that she’s quitting cosplay—or, at least, that’s the impression the cosclub gets. Next, Sanae and Ruth do a little dream diving. After that, Maki confronts Theia about some unexplained expenses she’s recording in the Satomi knights’ ledger. Then lastly, Shizuka recruits the entire Corona House crew to help out with the cook-off at the cultural festival. The girls will cook while Koutarou judges, and the results are explosive to say the least.

 The Satomi band of knights is steadily expanding and all is well in room 106. At least for a little while. Yurika comes to everyone with an unusually serious request—she wants them to help her savior and mentor, the former Rainbow Nana. Children then mysteriously start going missing in Kisshouharukaze City, which can only mean one thing. The evil magical girls of Darkness Rainbow are back in town and they mean serious business this time. Deadly serious business.

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.

With the coup d’etat back home in Forthorthe finally reaching critical mass, Elfaria and Theia decide it’s time for them to return. Theia is reluctant to drag her friends into the politics of her homeland, but they’re just as stubborn as she is. They band together and set out for Forthorthe, but their enemies will make sure not even the trip there is easy. They all have a long, hard fight ahead of them—and this is just the beginning.

Koutarou and company are left reeling in the wake of Ralgwin’s mysterious disappearance, but he isn’t the only cause for concern anymore. Maki receives an invitation from Rainbow Heart, which brings the whole group to Folsaria. All seems well at first, but intrigue and danger are brewing under the surface in the supposedly peaceful land of magic. An old enemy rears his head after ages, renewing a fight that Koutarou hopes to settle once and for all. Will he be able to claim a definitive victory this time with the girls’ help?

Lately, Koutarou has been growing more and more suspicious of Kiriha. Claiming that she's come to invade the surface is one thing, but what on earth is she doing helping the neighborhood association clean up the city? Is this all part of some nefarious plan? Or is there something else going on? When Koutarou works up the nerve to confront her about it, she responds by... asking him on a date?!

After the attack underground, Koutarou and company return to the surface to regroup and plan their next move. They know Ralgwin will continue to come after them as long as he still has a hold on Earth, leaving them little choice but to mount an offensive of their own in an attempt to put Vandarion’s coup to bed once and for all. Fortunately, they have a little extra help on their side with the arrival of Princess Nefilforan, known throughout all of Forthorthe for her military and martial might.

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?