Masumi is a teenage girl with dark skin tone, shoulder-length black hair and red eyes. She wears a small blue shirt with her LDS badge pinned on it over a cream one-piece long-sleeved shirt and shorts combination with black skin-tight shorts underneath ending above the knee, and blue boots. She carries her Duel Disk in a brown holster resembling that for a firearm. Masumi is a direct, straightforward and bold individual, showing little to no hesitation in saying what she believes. Due to her father's job and witnessing and appraising the value of jewels, she is seemingly capable of detecting talent and hesitation within people, as she did with Yuzu at the start of their Duel. Although Masumi shows a penchant for mockery, most of what she states is accurate thus, she does not act out of plain arrogance but on observation. She was not easily fooled, as seen when LDS Elites lied about Professor Marco being hurt in his Duel, and she was thus willing to seek the truth. Despite her bold exterior, she was visibly unnerved during her first meeting with Shun and when she saw the gouges that his monster had left in an overhanging road. Masumi is also a caring person, valuing her friends and her teachers, and after Professor Marco's disappearance, she became frantic in her attempts to find him. She cares for (and possibly has a crush) on Marco particularly, and doesn't tolerate insults towards him.