From Left to right:
Sko;Maci's Sparing partner and friend
Truun; The arrogant male who despises Maci
A'Lko Vorumee: The Teacher of Maci's, Skos and Truuns Class
Duran Nosolee: The wanna-be-rapper Ultra and Maci's and Truuns supervisor on their little adventure

All four of these males play a huge role, theres also a reason why Zuka isn't in this picture because he is mainly seen with Maci but also because in chapter 12 you will figure out another reason why he isn't in there too.