After returning from Okinawa, Shinya Yukimura and Ayame Himuro were unable to obtain evidence to support their claim of love for each other. They couldn't replicate the conditions they experienced during their trip, so they sought help from the Biological Sciences department at Saitama University. With assistance from fellow graduate students Chris Floret and Suiu Fujiwara, Yukimura and Himuro began to quantify their feelings by measuring their oxytocin levels in various romantic scenarios. However, they discovered that their love for each other was not as strong as that of a mature couple.
Chris then posed a question to both scientists: what would happen if their "affection" wasn't actually love? Yukimura became determined to find a scientific explanation for the difference and put all his efforts into proving that their love was real.