At age 12, Zayne's Ice Evol slips his control and nearly kills someone he cares about. The Death and Rebirth arc chapter 'Nightmare Genesis' (4-11) names that person as MC — she is injured and falls into a coma. His nightmares begin the same year, driving him to avoid sleep whenever he can. This event is the origin of his cold exterior and insistence on keeping distance: he genuinely believes he is dangerous and that he is personally responsible for the fragility she still carries. Three of his Anecdote arc chapters are literally titled 'Nightmare', 'The Nightmare Worsens', and 'Cover-Up' in reference to this ongoing guilt.