Chika Amatori's Side Effect

Short Summary
''After Osamu is expelled from Border, Jin meets him, and is introduced to Yūma, discovering Yūma is a Neighbor. Yūma then reveals that the irregular gates were being cause by a Neighbor, and Border makes an effort to find and destroy every last one of them. By Yūma's request, Osamu is given the credit for the information. Later, while waiting for Osamu, Yūma meets Chika Amatori, a mysterious girl who seems capable of feeling the presence of Neighbors. When a danger alarm sounds, Chika runs to the danger zone, and Yūma follows her, saving her from a Neighbor. Osamu, who became a B-Class Agent, defeats the Neighbor. Yūma then learns Chika's secret, and that she and Osamu already know each other, to his surprise.''

Adapted From

 * Chapter 11
 * Chapter 12