Onna Gokoro @Danshi Koukousei

Ren Yono is an ordinary high school boy whose hobby is writing novels. However, people criticized his stories for not understanding "the heart of a woman" due to his lack of romantic experience and female friends. One day, Yono gets his hands on a dubious online product that promises the user can understand a woman's feelings just by drinking it...!

(Source: Pixiv Comics, translated)