Rimu, who is set to graduate next year, has kissed her boyfriend Yuuta but hasn't gone any further. They had promised each other to wait until they were adults for a physical relationship. One day, when Rimu went to Yuuta's house to play, she met Yuuta's father Toru, who treated her like his own daughter. That day, the train stopped running and Rimu couldn't go home, so she ended up staying over. The next day, while Yuuta was out, Toru spiked Rimu's drink with an aphrodisiac.
