第 3 集: 椿在目睹幸平與阿由斗互動後，接受上葉的唾液以測試兩人的戀愛關係。
Tsubaki spots Kouhei kissing Ayuko Oka, who Kouhei explains is his girlfriend, whom he's been secretly dating for a while. When Tsubaki expresses his desire to kiss Urabe, she gives him a testtube of her drool, telling him to drink it before he goes to bed. That night he has a dream where he is accidentally kissed by Urabe, feeling disappointed that she isn't putting her feelings into it. The next day, Tsubaki comes to realise they should only kiss when they come to understand each other's feelings. Later at school, another boy in Tsubaki's class, Ogata, confesses to Urabe, asking her to go out with him. Urabe decides to give him a reply the next day, forbidding Tsubaki to interfere. The next day, she feeds Ogata some of her drool and, upon hearing he doesn't feel any different, rejects him. After doing the same with Tsubaki, which makes his nose bleed, because she was not wearing underwear that day, Urabe explains how his reaction to her drool is proof that he is the only one she shares this bond with, and they walk home together holding hands. (Source: Wikipedia)