Tsubaki is having a hard time wondering if he and Urabe are really in a relationship, and asks Ueno about what couples should do. He tries doing normal couple-like things but Urabe doesn't approve. However, Urabe has a plan that will help Tsubaki understand their bond. She takes him to an abandoned building and tells him to close his eyes. While they're closed, she shares her drool with him, which sends his heart racing. She had taken her clothes off and the excitement changed her drool, which is why Tsubaki became aroused.
As they walk home, Urabe tastes Tsubaki's drool and apparently sees the erotic dream he had about her the night before.