The yearly familiar exhibition is literally a day away and Louise is feeling rather depressed about it. Not only does Saito have nothing impressive to show off, but this year the Princess is watching as well, making it even more important. As night approaches, desperation sets in as Saito is unable to produce an act worthy of praise. A sudden mystery visitor turns out to be Princess Henrietta herself and her relationship with Louise is explained. The next day, Saito attempts a presentation only to be dragged off early by Louise. Walking away from the stage, they witness a robbery in progress by Fouquet and her earthen golem. Failing to stop her, Fouquet is able to run off with the fabled Staff of Destruction.

Worried that the princess may be blamed for Fouquet's theft, Louise volunteers to go out and catch her. With Kirche, Tabitha, and Saito tagging along, they travel to the last sighting of Fouquet with Longueville. There, they discover the hiding place of the Staff of Destruction only to have Fouquet's golem appear. Wishing to show her worth, Louise tries to take it head on with a spell, nearly being crushed in the process. Only by Saito's quick reflexes is she saved. Her confidence broken, Louise breaks into tears. Saito is moved by this and begins attacking the golem in her name. After discarding Kirche's sword and drawing Derflinger, the runes on his hands glow once again and his ability greatly increases. Louise tries to help by taking out the Staff of Destruction, which turns out to be a "M72 Light Anti-tank Weapon system(LAWs)" rocket launcher from Vietnam War. Immediately recognizing it, Saito grabs it and quickly uses it, blowing up the golem.

It's summer vacation and many students are traveling back to their families. Kirche goes along with Tabitha to her home on invitation, leaving Louise and Saito alone for once. However, mischief is still plentiful. Upset at Guiche's continued flirting with other girls, Montmorency creates a love potion and plots to have Guiche take it. Meanwhile, Saito obtains a large pot that was about to be thrown away and converts it into a makeshift hot tub, similar to the hot springs in Japan. While bathing in it at night, Siesta happens to pass by and much to Saito's embarrassment joins him. Seeing this, Louise becomes so frustrated that she interrupts Montmorency's plans by gulping the drink laced with the before mentioned love potion. As can be expected, when Saito returns to her room, Louise falls completely in love, causing many more problems.

The lovey-dovey antics of Louise under the love potion persist to the point of freaking Saito out. In desperation, Saito demands that Montmorency create an antidote. She refuses to do so until Saito learns of the illegality of creating love potions and threatens her with possible arrest. As the antidote requires the tears of a water elemental, Montmorency leads Saito and Louise to Lake Lagdorian. There, they find Kirche, Tabitha, and a whole new problem.

With the arrival of Wardes and Louise alone, they meet up with Prince Wales in a seemingly deserted church. After finishing up business, Wardes suggests to Louise that they should just get married right then. Confused and repulsed by the idea, Louise tries to refuse his offer, but one of Wardes' allies comes out with a mind-control ring, forcing her into agreeing. With the Prince as the minister, the marriage proceeds and is nearly completed until Saito bursts into the church. Snapping Louise out of her trance, Saito rushes to rescue her. In response, Wardes kills Prince Wales, revealing that he is in fact involved with the rebels fighting the government Albion called Reconquista.

The gang has located a rare dragon, which Siesta's family has kept a map. It turns out to be a Mitsubishi Zero-sen, a Japanese aircraft use in World War II. They bring it back to the school. Colbert said someone earlier used another aircraft to fly during the solar eclipse and disappeared. Saito concluded that the person returned home and this is his chance for him to return home also.

Cromwell launches an invasion on the day of the solar eclipse. Louise heads off to battle as Saito's chance to return home draws near.