After their unsuccessful attempt to scientifically quantify their love post-Okinawa trip, graduate students Shinya Yukimura and Ayame Himuro turn to the university's Biological Sciences department for assistance. With the help of Chris Floret and Suiu Fujiwara, a couple themselves, they delve into measuring oxytocin levels to gauge their romantic emotions. As they discover the depth of mature love, Chris challenges Yukimura and Himuro with the possibility that their feelings might not align with true love. In a quest for validation, Yukimura risks it all to scientifically affirm the authenticity of their affection.