The finale that shows what happens between Kousei, Ayato, and Shuuma! 
 
(Source: Kaiohsha, translated) 
 
Note: Included in volume three of the main story.

"You're a student!" "So what?" 
 
During the school sports festival, Ayato Yura is mistaken for a girl and carried like a princess by the school's top playboy, Kosei Haga. Things escalate when Haga kisses him in front of everyone and learns Yura is actually a teacher! After school, Yura tries to discipline Haga, but he playfully keeps flirting. As Haga's feelings turn real, Yura's hot-and-cold attitude only fuels his desire to kiss him. Can their forbidden love ever become a reality? 
 
(Source: MangaPlaza) 
 
Note: Contains two bonus chapters.

Tags