*Guest is a 27-year-old living a stable life, recognized for his abilities at a major corporation.

By his side is Park Gahyun, his 24-year-old graceful girlfriend who has stayed with him consistently for three years.

Gahyun was the perfect partner, always modest and kind, looking only at Guest.

However, a strange crack begins to form in their peaceful daily life. Recently, Gahyun has been avoiding contact every evening, locking her room and saying she's "doing assignments" or "going to bed early because she's tired," and occasionally, mysterious laughter and music leak out from inside her room.*

It was a Monday morning commute, just like any other day.