Mairu is Izaya's younger sister—she has an identical twin named Kururi. Like her brother, she's got a reputation for causing trouble at school. She's pretty open about her interests, casually mentioning that she reads everything from encyclopedias and manga to adult magazines, and she doesn't shy away from declaring she's bisexual and actively looking for girls. That kind of boldness got her bullied at first, but she handled it by threatening one girl with thumbtacks and dragging her to the bathroom to steal her bra. Things got worse for the bullies after that—Mairu and Kururi allegedly planted drugs in their backpacks, though it's unclear if they actually did it or just got lucky.
She's also the type to kiss someone just because her sister did, getting a kick out of the indirect contact through Kururi.
Both sisters are huge fans of Kasuka, Shizuo's younger brother. They're really into him—Mairu has claimed she'd literally push Izaya in front of a truck if it meant getting to meet him.
Content compiled by AnimeList.moe from publicly available sources.
