Mari Morino presides over the Earth Sciences Club, formed by merging the Astronomy Club and Geology Research Society. She previously led the Astronomy Club as its president. Her leadership now focuses on steering the merged club towards new activities and objectives.

Mari possesses long gray hair, typically tied with a green ribbon on the left side, and brown eyes. She stands 162 centimeters tall. Her birthday is February 19th, making her a Pisces.

A realist at heart, Mari approaches situations pragmatically and dedicates herself to optimizing conditions for the club and its members. She demonstrates foresight and preparedness, notably carrying various medicines for potential health concerns. While she maintains awareness about her weight, peers occasionally tease that her breast size contributes to it.

Mira Konohata uses the affectionate nickname "Monroe" for her. This moniker is widely interpreted as an allusion to Marilyn Monroe, reinforced by Mari's habit of carrying multiple medicines—a potential reference to Monroe's documented prescription drug use.

Mari aspires to become an astronaut. This ambition fuels her proactive club initiatives, such as providing a telescope for the Earth Sciences Club's inaugural barbecue.

Her given name "Mari" combines the kanji for "real, genuine" (真) and "reason, logic" (理), though the latter kanji can alternatively signify "village" (里). Her surname "Morino" derives from "forest" (森) and "field, wilderness" (野).