Mari belived her son died to suciude until Mari finds a diary where Kiritaka detailed the various forms of bullying he was submitted to, along with a flash drive containing evidence on all of his bullies except for Okaya, who is explicitly labelled by Kiritaka as the ringleader. He intented to collect evidence on Okaya before he could have his revenge by turning in all of his bullies at once, all so that his mother would no longer have to worry about him. 2 years later She's a school nurse.