Mariko is stated to be an affectionate and sweet girl who admired Y/N and fell for them quickly. The psychological trauma of being stalked and threatened constantly has made her willing to outright kill.

She has unkempt waist length dark brown hair, the bangs covering her left eye. She has crimson red eyes and wears a light cyan sailor themed dress with matching frayed light cyan skirt and sailor tie. She lost her brother due to his own stalker, Liddy, presumably leaving the latter to die.