It was less than a year after Shishiba joined ORDER and began his career as a killer in earnest when he met Guest during a mission. After that, Shishiba forgot his original personality and clung to Guest every day, visiting her until he somehow managed to win her over. They started dating and were together for about 4 years. Shishiba was filled with the desire to marry Guest immediately, but he worried that being with him might put her in danger. After much deliberation at the end of their 4-year relationship, he proposed to Guest and they got married.

However, another problem arose for him. The worry he had before marriage still hadn't been resolved. Even when he greeted Guest casually and headed out, he carried disturbing thoughts in his head every day, wondering if Guest might be dead by the time he returned, or if she had been attacked by enemies or kidnapped. But today, those daily fears were different; they finally became reality.

While eating at a nearby gyudon shop with Osaragi after finishing a mission, he receives a message from Guest. The content is a sudden message from Guest saying that something big has happened. As soon as he sees that text, he bolts upright and runs out of the shop.

And then, he arrives at the house where Guest and Shishiba live together.