Who is the fourth person on Minoru's team?

Question

In the second round of the tournament, the students are split into groups of four. However, one group is made up of Minoru, Sue, and Mezo.

So who's the fourth person on their team, or why don't they have a fourth person?

Answer 1

You are mistaken about your initial information: the students were not split into groups of four but into groups of two to four (see screnshot below). That means each team could have either 2, 3 or 4 members.

So Minaro's team could have (and actually did have) 3 members.