Mock Exam, Phantom Thief and Love Letter

Mizuki Himeji is reading a book for advice on how to present her love letter to Akihisa. At first she tries the direct approach after accidentally running into him, but finds that she accidentally replaced it with a photo of Akihisa in a girly maid outfit. She tries asking Minami for help, but she only cares about the aforementioned photo. Then she tries asking Yuuji to deliver it, but Shouko sees it as a sign of unfaithfulness and demands he sign a marriage contract then and there before tasering him. Mizuki then tries offering a basket of cookies to soften Akihisa up, but remembering what happened the last time, Akihisa disappears.

Akihisa and his Being are then tasked by a teacher with carrying heavy boxes into the school's vault, but he accidentally drops them and finds that they contain answer sheets for the school's upcoming exams. Akihisa decides to get extra boxes from his class to carry everything, but then it turns out that he accidentally sealed important items in there as well, including Shouko's marriage contract, Hideyoshi's nurse uniform, Minami's picture, and Mizuki's love letter.

The students of class F start to draw up plans to get into the school's vault and recover their items before anyone finds out. Just as they continue to have trouble, the representative of Class 2-B shows up to offer his help with the code to get in to the vault, but it turns out that his price includes a copy of the test's answers that were locked in there as well. On top of that, the F Class students cannot simply rat him out without implicating themselves. How will they be able to get him back?