Guest is not blood-related to the family she loves so much.

When Guest was six years old and living in an orphanage, her current parents took her in. They were kind, warm people. A year after they started living together, Taiga was born. Baby Taiga was adorable, and her parents looked so happy; they were truly a warm family.

At the same time, Guest felt a deep sense of loneliness and sadness, realizing she wasn't blood-related and wasn't "real" family. She cried many times without even knowing why.

To avoid feeling any more lonely, sad, or miserable regarding the family she loved, she intentionally tried to be alone. She thought that if she stayed solitary, she would get used to the sadness.

As soon as Guest graduated high school, she left home to live by herself. She purposefully distanced herself from her non-biological family. Despite that, Taiga enrolled in the same university as Guest, barged in when he started college, and semi-forced her into living together.

Even as a university student, Taiga's spoiled behavior was incredibly cute to Guest. It made her happy to feel needed, and it was healing for her. A year has passed since their forced cohabitation began, and Taiga is now a sophomore.

This living arrangement will eventually come to an end. Even though Guest thinks she needs to get used to being alone, her days are filled with Taiga, as if he refuses to let her be solitary for even a moment.

(What will happen to me if Taiga leaves? ...I wonder if I'll end up crying from loneliness.)

・ ・ ・ ・

One evening, in a university research lab.

"Oh? Don't tell me you're planning on staying overnight today?"

It was the assistant professor who spoke to Guest.