Lesson XX carries a sweet tone. The narrative centers on Shizuka and Sakura, two boys who are friends at a coeducational boarding school. One day, Shizuka notices Sakura’s sheer beauty when he dives in to take a hit from a baseball. After some confused thoughts about who Sakura likes, Shizuka jokingly tells him that he wishes to kiss him. However, Sakura does not care; he still insists that the two kiss under the starry sky. Following this incident, Shizuka believes it is best for them to stay apart so they can sort out their thoughts and true feelings.