Proof 2: Love Has Fallen In Love, So We Tried To Measure The Heart Rate (理系が恋に落ちたので心拍数を測ってみた。, Rikei ga koi ni ochitanode shinpaku-sū o hakatte mita.) is the 2nd chapter of the Rikei ga Koi ni Ochita no de Shōmei Shite Mita (manga) by Alfred Yamamoto.
Shinya stopped Ayame, placing his hand on the wall behind her and telling her to not run away as they were in the middle of an experiment. He then backed away, explaining they just did the "kabe-don" (wall-pinning) behaviour and asked her how it was. But Ayame told him it was questionable, as she found hollowness in his trembling voice and that he obviously wasn't used to this. Little annoyed, Shinya told her he wasn't asking about that, but about her beating heart rate. Ayame looked away and then Shinya took her hand to see her heart rate being 147. Seeing this, he told her that while she was complaining, her heart rate was quite high, but Ayame quickly avoided the subject and told him that if they use this experiment, they can find out if she liked him or not. In the same time Kotonoha was observing them and wondering what was wrong with them.
A day earlier, before the current experiment, Ayame and Shinya were telling Kotonoha about the experiment they will do to find out if they loved each other, showing her Ayame's graph. Ayame then asked Kotonoha when she thinks is in love and Kotonoha showed her a "kabe-don" behaviour saying that her heart rate starts to beat faster when it happens. Since faster heart beat was in the pie chart, they conducted that measuring the heart rate will help them quantify the numbers the effect of love.
As they got a heart rate meter, they measured the running, walking and staying calm heart rate of Ayame. They tried to measure it away while she was sitting and Shinya was next to her, but her heart rate started to increase. She asked Shinya to back off, but even at some distance, her heart rate didn't decrease. Then they considered making a situation you do with someone you love, but since both didn't had love experience, they didn't know what to do. They tried searching it over the internet, but since they didn't specify for being in love, they tried some methods are normally used for different things, like lifting her chin or rolling her sleeve. Ayame then realized something and asked Shinya to remove his eyes, as she blushed she confirmed her hypothesis, but didn't reveal what was it. As Shinya conducted the more close they are, her heart rate is faster, she hugged him and suggested they stay like this for a bit. Ten minutes later, Ayame had fallen asleep and Shinya was wondering what he have to do in that situation, but also found he enjoyed her scent.
Back at the university, they showcased to Kotonoha a graph from the experiments they did and in each Ayame had increased heart rate. Kotonoha noticed Ayame's heart rate was quite relaxed at the end of the graph and wondered why, but Ayame didn't told her. Kotonoha then overjoyed conducted Ayame must then love Shinya from her heart rate. But Shinya told her to not rush to conclude things. He then showed the manga Kotonoha showed with the "kabe-don" scene and commented that at first it looks like the girl is in love, it also could be premature menopausal disorder. Ayame then explained that there is a variety of reason a heart rate can increase and in that scene it could be due to the "kabe-don" or for example the girl seeing an UFO. Hearing this, Kotonoha thought that then no matter how many experiments they do, they won't be able to conclude anything. And that they should continue to experiment and maybe do 20 "kabe-don" situation and that they may also measure Kotonoha's heart rate too.