A boy shows up for class in the fall. Everyone thinks he is a new student. No one suspects that he was a female classmate of theirs last spring. The girls think he is 'oh so cuuuute'. The gay boys see him as a target. Even some of the straight boys do a double take. Then along comes role call in homeroom on that first day. When the teacher calls out, 'Traci Cole' and he replies 'present' everyone's head spins around to look and they finally see the facial resemblance to the ex-cheerleader who was now a skateboarding boy. This would be MC.
YC could be male. You could be female. You could be one of each. Two of one and so on and so forth. Maybe even another FtM.