Death: one of the two dies and this is all just a retelling of his memories regarding the situation.
Accident: one of them gets really hurt from some kind of accident or fight.
Abandoning: one of them just can’t take it anymore and abandons the other, either to protect them or from fear of the relationship.
Jail: someone’s gonna harm someone in a way that’s gonna get the police involved. MC’s dad is the more likely person but I wouldn’t put it past the “friend” to start something. (Like I could see a scene where someone pulls a knife, MC’s dad gets killed or MC/ML gets stabbed but the blame gets pinned on the other.)
Amnesia: more accident leaning and they just forget the other person so that causes that person to leave in order to avoid getting them further harmed.
I was nervous one of them would run off and complicate/drag things on more but LUCKILY they just went for it and KISSED.
Now I’m worried over the past tense phrasing. Death, an accident, amnesia, abandoning, maybe jail? (Some kind of time skip is gonna happen and I’m scared to know in what manner.