She's often spoken of as being kind and gentle, and plays a sisterly role in the friend group with SUNNY, HERO, KEL, AUBREY, and BASIL. Her first appearance shows she has a mischievous side, poking fun at KEL and AUBREY's mannerisms and afterwards teasing HERO. These traits are shared with her HEADSPACE counterpart.

Later in the game, it is also revealed she would pull pranks on HERO especially, such as putting bugs in his school desk. It is also shown that she was a perfectionist, spending hours at a time practicing the same piano piece over and over again.

Even after her death, her spirit form is shown to be forgiving towards SUNNY despite what he did to her. She also tries to help SUNNY forgive himself and reminds him to remember what's important. Despite knowing that her brother accidentally killed her in the past, MARI wishes for SUNNY to move on and live out his life without any regrets.