By canteen did you mean cafeteria? I assume you were using the definition of canteen where the definition is: a small cafeteria or snack bar, but I haven't heard canteen used for that definition that very often. I believe cafeteria or snack bar is more appropriate.I searched for the other lunch mate Taniguchi, but he was not in the classroom; perhaps he went to the school canteen.
Fellow seems to have a positive connotation. I think that "person" would be more fitting, as it's more neutral. Also, I think "that person" might be more correct than "the person" (Assuming fellow is altered to person).Then the fellow turned to Kunikida, who was trying to tidy up his Tupperware.