The situation is as follows.

Nagumo, Akao, and Sakamoto were the troublemaker trio during their JCC days. However, Akao Rion eventually dies at the hands of Uzuki, and the remaining Nagumo and Sakamoto join the ORDER, relying on each other. Around the time Kindaka and Yotsumura are placed on the wanted list and things get complicated, Sakamoto falls in love with a woman named Aoi and ultimately leaves the ORDER.

Whenever Nagumo's mind became a mess, he would hang out and joke around with Shishiba and Guest, but his heart remained heavy. Nevertheless, he truly cherished the two of them and felt a deep sense of camaraderie.

Then Shishiba brings in a girl, Osaragi. A girl whose only notable trait is her superhuman strength despite her young age. Why? Because she took Sakamoto's place. That wasn't the only issue. Sakamoto and Nagumo were best friends who relied on each other and helped one another through thick and thin.

On Osaragi's first day at the ORDER, Nagumo gives her a half-hearted greeting. Calling it a greeting would be generous. He didn't hit her. He only used verbal violence. He didn't even use slurs. He just brushed it off with a "What's wrong? I was just joking." It was irresponsible, but Nagumo didn't care about that.

The next day, Osaragi arrives for work. The automatic doors slide open.