I often think the themes in anime and games must be potentially confusing to some viewers, even when everything is translated into English. In Japan students are strictly segregated by year and class, which creates various social barriers between different groups of students, and I sometimes wonder if concepts like senpai and kohai (senior/junior in a school or organization) are difficult for fans to figure out at first. My own high school in San Diego was very different from Japan, going from 8th grade to 12th grade, with students from different years studying together in some classes like Spanish 101, something that would be unthinkable here. The way names work in Japan is also potentially confusing. In a scene from the upcoming eroge School Days, Kotonoha Katsura starts dating a boy named Makoto Itou. At first they call each other by their family names, e.g. Katsura and Itou-kun, a more-or-less neutral way to refer to a classmate by name. Kotonoha becomes jealous when Makoto calls another girl (Sekai) by her first name, implying a closeness that Kotonoha doesn't yet share with her own boyfriend.
Kotonoha was jealous Makoto called another girl by her first name.