WARNING: The following contains spoilers for The Irregular at Magic High School Season 2, Episode 10, "Visitor Arc X," now streaming on Funimation.
Despite being one of the world's most powerful magicians, Lina -- aka USNA Stars Commander Angie Sirius -- has failed both of her primary missions in Japan: execute all the USNA military deserters (or Vampires) and apprehend or eliminate the magician behind the Scorched Halloween incident. After losing high-stakes battles to both Miyuki and Tatsuya, she is now thrust into a position where working together against the parasites is the ideal option.
Thanks to Raymond Sage Clark's message about where the parasites will gather next, Tatsuya and friends go to the designated spot near First High School's campus. Now that they know how to seal the parasites inside their host bodies, it's the perfect chance to contain their long-term threat. Unfortunately, Lina cannot put her anger and resentment aside, making everyone else's jobs more difficult and forcing Tatsuya and Miyuki to reveal a huge secret about their magical abilities.
Tatsuya, Miyuki, Erika, Leo, Mikihiko, Mizuki, Honoka and Pixie all arrive at First High ready for battle, each knowing his or her specific role. The parasites want to retrieve their rogue comrade, still inside Pixie's body. Tatsuya learned from previous fights that destroying a parasite's host body does not stop the parasite itself from escaping. Rather than try to kill them outright, the group's goal is to knock the host bodies unconscious and seal the parasites inside. Everything is going according to plan -- until Sirius shows up and burns one of the bodies alive. Tatsuya asks her to stop, but Lina counters that she is following her assigned mission: to execute the USNA military deserters, some of whom happen to be the parasites' host bodies.
Lina is only following orders, but her actions directly allow the parasites to escape and grow even more dangerous. Her pent-up negative feelings have affected her judgment, which once again shows a crucial difference between her and Tatsuya: while she furiously races into battle alone, Tatsuya continues aiding her while calmly informing his teammates when to do their part. Mizuki uses her unique eyesight to track the parasites' movements, Mikihiko uses Spirit Magic to trap them in place, Erika strikes the host bodies down with her sword skills, and Tatsuya attacks the parasites within.
Though Erika also prefers to kill outright, she and Tatsuya put their differences aside for the greater good. Lina's differing goals didn't have to result in conflict, but she's feeling angry, hurt, and isolated. She may be the USNA's most powerful Strategic-Class Magician but she's also a lone teenage girl on military assignment in a foreign country. The people she wanted to befriend are the same people her job forces her to oppose.
After being chastised by Miyuki, Lina rushes back in to battle the escaped parasites herself. While she's unable to harm them, she forms a powerful shield that distracts the parasites long enough for the others to help. Tatsuya and Miyuki perform a rare and powerful spell that combines their abilities in body and soul: Lunar Magic, a type of Interference Magic that directly targets a being's spirit. Together, the spell allows them to find and weaken the parasites directly at their core. With a final enormous ice attack from Miyuki, the parasites are destroyed once and for all.
While the siblings are aiding Lina, Erika and Leo find surprising resistance from a group of National Defense Force agents who are there on behalf of Retsu Kudou -- the patriarch of the Ten Master Clans. Like the Yotsuba Clan, Kudou has long been watching Tatsuya and the other factions' progress in battling the parasites and has decided to make his move. Pixie aside, two other parasites remain alive and safely sealed inside their host bodies. Ayako Kuroba -- once again representing the Yotsuba -- and Kudou each agree to take one parasite for themselves. The Yotsuba's goal is likely to study the parasites and utilize them in pursuit of more power. Kudou's goal, like the man himself, is far more shrouded in mystery.
After the battle, Tatsuya warns Lina to tell no one about the Lunar Magic spell she saw. She agrees, and he in return will continue to keep her Angie Sirius identity a secret. Despite their many conflicts and opposing ideologies, Tatsuya still sympathizes and relates to Lina's situation -- a young powerful magician being largely isolated and forced into military duty without any real say in the matter. He extends an olive branch, offering to help her leave the USNA military. A stunned Lina isn't inclined to accept right now, but she has a lot to process after many hard lessons in Japan. For now, at least, she and Tatsuya have finally reached an accord.
