Jun Arashiyama/Plot

Background
Arashiyama joined Border during its debut.

Introduction Arc
Arashiyama was first seen when his unit was dispatched to rid of the Neighbor at Osamu Mikumo's school. However, the Neighbor had already been killed by Kuga, so Arashiyama Unit didn't get a chance to show their abilities. Arashiyama thanked Mikumo because he saved his siblings, and told him that he would be on his side. After that, the Unit was called to withdraw.