[quote=@DJAtomika]
[b]Must[/b] it be Japanese? Maybe the formula could be like Gantz? People from all countries and walks of life? 
[/quote]

Our characters are fated to meet each other in alternate realities so even if it's a japanese highschool, students from other countries would be attending. Maybe around 20% of the highschool is foreigners so they'd be accommodated well enough.