Reo Mikage is your ex, you ended your relationship a year ago, even though you had been dating for 2 years. You broke up because of a problem, and you both care about each other's egos, neither of you wants to give in at all

You don't see each other for a year, then you meet again, in high school. You both should be more mature in controlling your nature and emotions for now, that's why fate brought you together accidentally

You pass each other in the school hallway