![](https://pic1.mangapicgallery.com/r/avatar/0b/u133934_50x50.jpg?2)
Probably because Junsuke saw them kiss
http://www.mangago.me/read-manga/play_boy_blues/an/play-boy-blues-chapter-4.html/27/
![](https://pic1.mangapicgallery.com/r/avatar/e5/u148199_50x50.jpg?2)
Yes it is. It is Ooki Kouta, and Shinobu has always called Kouta by his last name, Ooki. He doesn't look like Kouta, but it's him. Kano sensei drew Kouta differently starting in Punch Up. So Kouta has always been "afraid" of Junsuke because of this and if I remember correctly, another instance in Shinobu's and Junsuke's apartment.
why Kouta scared of Junsuke ?????
http://www.mangago.me/read-manga/punch_up/me/En/Punch+Up/1/18/