Aoi Sakurai

She is part of the Tokyo Railroad Security Force under the "Fourth Peacekeeper Squad" or K4, she is a crack shot and a proficient fighter, however, being the most aggressive member of the squad, she is easily bored and always yearns for some action where has no hesitation when facing danger. She is also a man hating tsundere who enjoys mocking Naoto very harshly because she simply sees his presences as annoying.

[Spoiler] Despite her attitude, she seems to develop feelings for Naoto. [/Spoiler]

(Source: ANN)