Während Henrietta dazu gedrängt wird, Albion den Krieg zu erklären, helfen Louise und Saito Julio und Agnès dabei, ein geheimes Archiv hinter der Schule zu finden, in dem Agnès Informationen über die Zerstörung ihres Heimatdorfes vermutet. Als Siesta zur Gruppe stößt, sorgt Louises Eifersucht wieder für eine Explosion, die der Gruppen den Rückweg aus dem Tunnel versperrt...
Henrietta is convinced to sign a declaration of war against Albion. News of a victorious battle for the Tristain and Germania allied forces reaches a town that Louise and Saito are currently in. Saito discovers a sailor uniform on sale at a clothes merchants shop, and buys it, opting to give it to Siesta rather than to Louise. Upon returning to the academy, the two join Agnes and Julio on exploring a secret archive hidden beneath the school, which Agnes was denied permission. Agnes wishes to obtain the information there regarding her home town of D'Angleterre's burning to help carry out her revenge against those involved. Eleonore is picked to open to lock to the entrance. As the group heads farther down, they are joined by Siesta, who is wearing the sailor uniform Saito gave her earlier. After discovering that Saito gave the sailor uniform to Siesta because Louise lacked the chest size to make it look good, Louise blows a part of the cave in the way they came. With little to do but move further, the group finds the archives and are sent to look for the records regarding the town of D'Angleterre's burning 20 years ago. When Siesta trips and makes a mess of the books, Eléonore returns them to their proper place with magic, which triggers the archives' security system and begins to bring the bookshelves to a close. Agnes finally finds the information regarding D'Angleterre's burning, but a part of the page that lists the person who led the attack is missing. The group narrowly escapes the collapsing of the bridge that led them to the archives. Upon realizing that Louise had blocked their way out from before, Julio grants Saito permission to have intimate moments with Siesta. Siesta is happy to oblige and Saito also thinks it to be a good idea, however, Louise is watching and is preparing to blow something else up. When Saito points out that the cave in she made earlier is in the opposite direction, Louise tells him to shut up and blows them up anyway.
Tristein dichiara guerra ad Albion e le operazioni militari procedono bene. Prima di raggiungere il fronte però Agnes vuole trovare alcuni documenti inerenti una presunta ribellione soffocata nel sangue venti anni prima e racchiusi nell'archvio segreto posto sotto l'Accademia. Ma anche questa volta Saito riesce a far infuriare Louise, la quale fa esplodere il passaggio bloccando la via del ritorno.
トリステイン連合軍とアルビオンとの戦況が激化を辿る中、アニエスは前線に赴く前に、自らの忌まわしき過去「ダングルテール事件」について調べるために魔法学院の地下にあると言われる極秘公文書館の閲覧を申し出る。しかし危険だという理由で学院長に申し出を拒否されたアニエスは、ルイズやエレオノールたちに密かに入口の鍵を解除してくれるよう協力を依頼する。しかし、才人からプレゼントされた水兵服に着替えた姿を見せようと才人の後を追いかけてきたシエスタのせいで、ルイズが激怒してしまう! いつもの大爆発で地下の迷宮に閉じ込められてしまった一行は、出口を探すために地底を彷徨い歩くことに…。
La princesa Henrietta declara oficialmente la guerra al reino de Albion, luego de que le comentaran que si no aceptaba firmar el documento podría sufrir un golpe de estado en Tritain, puesto que toda la nación quería combatir.
平定了里修蒙之亂後，漢麗塔在不得已之下對亞爾比昂宣戰了。沒想到開戰不到1週，就得到了首次的大勝並佔領了重要的對外空港。艾格妮絲在漢麗塔要親征前，取得她的同意，來到學院地下秘密公文保管室，一行人會在那裡發現什麼真相呢?
