"My Bloody Valentine" is Chapter 10 of Tsurezure Children. It is centred around Alice Himemiya and Haruhiko Takase.
Valentines is approaching, and Alice wants to make homemade chocolate for Haruhiko. She wants it to have extra love in it, so she cuts her hand as blood pours into the mixture. On Valentines day, Alice is about to give Haruhiko her chocolate, when Saki gives Haruhiko her's, claiming it's just friendship chocolate. Alice catches on, seeing how it isn't just "friendship" chocolate. Alice finds this heartbreaking as to how her rival is so cute, and threatens to kill herself with a box cutter because of it. But before she does, she thinks of how she wants to die in front of Haruhiko, as she stops herself. Before she can put the cutter away though, Haruhiko walks around the corner to see Alice holding it.
Alice quickly runs away, sneakily stealing Saki's chocolate from Haruhiko's pocket, and runs to the bathroom. Alice opens up the chocolate, finding a love letter accompanied with homemade chocolate. Alice smiles, thinking how cute Saki is and how they could be friends. Although, she flushes the chocolate down the toilet. Alice gives back the chocolate, as Haruhiko opens them, only to find them empty. Alice acts surprised, telling Haruhiko that Saki probably forgot to put the chocolate in. Alice tells Haruhiko that if Saki asks what he thought of them, he should say they were good.
Haruhiko smiles, telling how nice Alice is and whoever got Alice's chocolates is lucky. Alice tells him that he shouldn't tease her, and how she'll be hurt if he doesn't mean it, as she turns around, and pulls out her box cutter. Alice then gives her her chocolate, that is accompanied with a note.
Marriage registration form. Haruhiko politely rejects them, as he gives them back. Alice is surprised, but she couldn't muster the courage to tell him the chocolates her for him, so she gave him her backup chocolate.