39 Setagaya Ward, Tokyo

A certain summer day. Mika Shiota, a company employee who always works silently in the corner of the company. Even though it's midsummer, the office is still very cold today because somebody has cooled the AC. Therefore, she wants to go to the restroom immediately. Mika heads to the restroom, but all are in use. Despite the limits of patience, visitors have come. "It is impossible now!" Mika goes to the restrooms on every floor of the company building, but all are locked! I just can't stand it anymore! At that time, the forbidden door is reflected in her eyes. On the other hand, Mika's subordinates are preparing cold tea to serve visitors. He has poured tea into the glass and seems to overflow at any moment.

Yukiko, an assistant to a fashion designer, goes to a language school to study abroad and has a relationship with a male teacher. Dreams and reality slowly become one, and Yukiko loses her mental balance. What really scares her is whether "Sensei" really existed.