When Ami receives a love letter, she states that she does not have time to worry about love because of the upcoming high school entrance exams. Ami has been getting all 100% on her practice exams, but another mysterious student named Mercurius is getting all 100% as well. Ami believes this is a challenge by a new enemy, but also comments on how passionate a rivalry feels, and begins to think about Mercurius obsessively. A being named the Terayoka, a woman who feeds on the desires of others, notices this and attaches herself to Ami. Later, Ami is in bed sick, as the Terayoka is finishing her magic. Ami suddenly overcomes it, transforms into Sailor Mercury, and defeats the Terayoka, believing she was Mercurius. However, an investigation by the other Senshi reveal that Mercurius looks almost exactly like Umino.