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.

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.

Having taken care of the love potion, a new problem arises again. This time, Princess Henrietta is to be wed to the Emperor of Germania for the sake of backing up the smaller country with a stronger power. In order to do so, a certain letter the princess sent to Prince Wales of Albion. If it is ever publicly revealed then the marriage would be impossible. At the moment, Albion is in a state of civil war, so Henrietta herself cannot see the prince. Therefore, Louise is sent with a message to Prince Wales requesting that the letter be retrieved. Guiche then enters, revealing that he had "accidentally" heard it all and would be willing to aid the princess. Much to both Louise and Saito's ire, Henrietta accepts Guiche's offer. On the day of departure, the escort arrives and is revealed to be Wardes, Louise's fiancé. A growing jealousy develops in Saito on the way to the port city of La Rochelle.

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.