It has been so long.. Who is that dude?

La posible manzana en discordia

I think you mean "la posible manzana de la discordia"

Yep,después me di cuenta.

Can anyone please tell us where the soccer dude shows up?? The chapter where he first shows up

here http://www.mangago.me/read-manga/hidamari_ga_kikoeru/bt/manga/hidamari_ga_kikoeru/c013/pg-4/

thanks so much!(づ￣ ³￣)づ