When Himuro finds out that her junior in the Ikeda lab, Kosuke, has spent over 220 thousand yen on his beloved Aika and holds her every night when he goes to sleep, she is shaken by the realization that the only present she's ever given Yukimura is a notebook, and that she's never held him while she slept. She worries that she can't objectively call what she feels "love." As Yukimura and Himuro endlessly debate "love" using numbers, Kanade proposes that the two of them go on a date, but...

Yukimura and Himuro wear lab coats, as befits science-types, as they get ready to begin their date experiment. Kanade is there to watch over their date and record observations, but she can't help bursting in to tell them to buy date clothes. Both of them are wearing monitors for heart rate, blood pressure, and temperature, and they're using an app to record things like "times my heart raced," "times I felt happy," "times I felt relaxed," and "times I felt uneasy." Suddenly, a man appears and starts hitting on Himuro...!?

Today is a day when the members of the Ikeda lab gather to announce research results. When Kosuke cites Aika as an excuse for not having read the papers he was supposed to, Professor Ikeda's muscles expand and he crushes a pen to smithereens. On the other hand, Yukimura and Himuro give a joint presentation of the results from the date they went on. As they present the records stating in which situation their highest recorded heart rates were, writhing in distress with the embarrassment, Professor Ikeda's reaction is... On top of this, In order to increase the amount of experimental data, Yukimura and Kosuke, and Ibarada and Kosuke, form pairs to measure data on their vitals...

Ibarada suggests that one of the greatest factors in the base conditions of romantic love is "whether or not you want to kiss the person," so Yukimura decides to try to kiss Himuro. However, Himuro doesn't like the idea of a kiss where the exact angle is measured with a protractor. When Himuro realizes that if the mood were more like it had been in the Ferris wheel, she might not mind a kiss, she and Yukimura create an equation to numerically define "mood value." In what location might the "mood value" be highest? And will the two of them be able to kiss...?!

The first semester has come to a close, and the Ikeda lab is having a party where everyone's bringing what they like to eat and drink. They're having fun, playing games like the "prime number Yamanote line game," when a drunken Himruo finally does a certain something with Yukimura... And even Kanade ends up drunk... On the other hand, the mood quantifier obtained through the previous round-robin kiss experiment has progressed their research tremendously, and in order to gather more data, Yukimura and the others use fairy tales such as "Snow White," "Kaguya-hime," and "The Crane Returns a Favor" as references, but...

Yukimura and the others will be giving presentations at the summer study sessions. There's less than a month left until the training camp, but Kosuke still hasn't picked a research theme. Professor Ikeda suggests research into "an algorithm that could instantly find the True End in any dating game." On the other hand, Yukimura and Himuro are focused on the hormone which is released when a person is touched by someone they love - oxytocin. By investigating the amount present in a person's saliva, they think they might be able to determine if the person loves the one who touched them, and they decide to immediately put it to the test with some close contact...

At long last, it's the first day of the summer training camp. On the plane, Yukimura presses close to Himuro and tries to collect her saliva in spite of the surrounding gazes. Manga artist Yamamoto observes them with an eerie smile. On the beach in Okinawa, the midsummer sun shines down on Yukimura and Himuro in their swimsuits, and they immediately attempt to begin their close physical contact experiment. However, since they're doing it, they choose to seek "the position which offers two people having close physical contact the greatest contact area"...

As Himuro looks out over a sunset colored ocean from her room in the resort hotel, Yukimura barges in saying, "we have to do now what we couldn't do this afternoon." The next day, it's finally time to make their presentations in front of a huge audience. Kosuke boldly gives his presentation on romantic visual novel games, but one of the professors grills him, asking, "what purpose does this research serve?" On the other hand, when Kanade falls into a panicked state just before her presentation, Yukimura hugs her, not realizing that Himuro is watching.

Kanade finishes her presentation safely, but when she goes backstage, Yukimura and Himuro are fighting. Before her presentation, Yukimura hugged Kanade, trying to help calm her anxiety. Out of jealousy, because she hasn't been able to do any close contact experiments with Yukimura lately, Himuro ends up saying some very harsh things to Yukimura. In return, Yukimura finds himself replying, "it isn't as if we're dating, is it?" The heartbreaking statement causes Himuro to race from the room. Having witnessed this scene, Yamamoto smiles an eerie smile...

For some reason, the glasses case Himuro gives Yukimura as a present is smashed to pieces. Shock sends Himuro racing away from the scene. Ibarada points out that it could have broken when Himuro fell on the stairs, but Yukimura estimates the force of impact based on the case's mass, materials, and height of fall, and concludes that someone must have deliberately destroyed it. Finally, at dawn, Yukimura finds Himuro crouched alone, barefooted, on a bridge. Will they be able to reconcile? And will they be able to prove their love...?!