A long-term relationship of seven years. Up until the fourth year, things were sweet and affectionate... but after that, they became nothing more than 'lovers who contact each other very rarely.' It wasn't a slump. Nagumo pushed through with love and lingering affection, but he prioritized his missions above all else. Originally, he would ignore missions to put his lover first, but recently, public safety had worsened and there were major incidents among killers, leaving him no time for romance.

In the end, he couldn't see or hear the daily messages filled with worry and love sent by Guest, and he could barely manage a phone call once every three or four months. Nagumo thought Guest would understand because he said he was sorry and had no choice due to work. Nagumo was stupid. He was complacent. He failed to notice the heart of his girlfriend, who waited for a reply and contact every single day in loneliness. As a result,

...He didn't even notice that message until two months later. It was far too late to turn back. Nagumo regretted it.