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Valentine's Day is War (バレンタイン is WAR.Barentain is WAR.?) is the 1st chapter of the 8th volume and the 53rd chapter overall of the Attack on Titan: Junior High manga, written and illustrated by Saki Nakagawa.
The day before Valentine's Day, Mr. Smith warns the male students to not expect any chocolates tomorrow if they arrive at school. This sends Reiner, Bertolt and Jean into shock and dismay, but they decide to try and tough it out. The three try their best to resist the urge but when other male students begin getting chocolate throughout the day, it becomes almost unbearable.
Summary
On the day before Valentine's Day, all of the students of Attack Junior High School are summoned to the school gymnasium. There, Mr. Smith warns all of the boys that if they come to school tomorrow hoping to get chocolate, they will likely die, causing many of the boys in the audience, including Jean, Bertolt, and Reiner, to panic. Mr. Smith asks them all to imagine different scenarios in which they do not receive any chocolate on Valentine's Day, making many of the students writhe in agony. Jean says that he does not care about getting chocolate. However, Mr. Smith tells Jean that he especially should not come to school tomorrow since boys like him are in the most danger. Jean and the others ignore Mr. Smith's warning and show up to school on Valentine's Day anyway.
On Valentine's Day morning, Jean checks his locker and is disappointed not to find any chocolate inside. Hannah shows up and gives Franz a gift of chocolates, making Jean jealous. Connie opens his locker and does not find any chocolate, either. Connie asks Jean if he got any chocolate, to which Jean replies that he found exactly what he expected. Jean then remembers promising Mr. Smith that if he did come to school, he would not feel sorry for himself if he did not get any chocolate. Jean goes to class to find Mikasa delivering chocolates to Eren, who dismisses her and wonders why she even bothers giving him any.
In Reiner's class, Krista arrives and gives Ymir a bag of chocolates. Ymir notices Reiner eavesdropping and screams at him. Reiner says he was hoping Krista would have something for him, but Krista confesses that she brought no chocolate for him, crushing his spirits. Krista notices that Annie brought lots of chocolate, too. Bertolt watches in anticipation, but when it is revealed that the chocolate is for Eren, he joins Reiner in self-pity. The two join Jean in a storage room, where the three of them seethe over not getting any chocolate.
Marlowe begins to eat some chocolate he received from Hitch, but it causes him to pass out since Bertolt laced it with sedatives. Outside, Petra shyly gives some chocolates to Oluo. Before Oluo gets a chance to return the affection, Reiner attacks him from behind with a garden shovel. Back inside, Eren finally comes to his senses and thanks Mikasa for the chocolate she made for him. They are about to share some of it, when Jean, Reiner, and Bertolt show up with weapons. Before the three can land a successful attack, Mr. Smith intervenes and stops them.
Mr. Smith reminds the boys of his warnings, to which they all confess to being upset over not being given any chocolate. Erwin points out that none of the boys even tried to get any chocolate. The three then look outside to see plenty of their fellow male students begging girls for chocolates. Out of pity, Erwin gives each of them gifts full of chocolate. Nile comes to tell Erwin that he missed a meeting. Jean, Reiner, and Bertolt begin bragging about the chocolate they received, but Nile reveals to them that all of that chocolate, which Mr. Smith could not finish, was given to him by his female students.