Masachika was a young man with an average build and short, spiky black hair. He had noticeably small, rounded eyebrows and two prominent scars on his left cheek. His mouth was usually curved into a happy smile.
Masachika wore the standard Demon Slayer outfit that consisted of a dark gakuran jacket, white belt, and baggy hakama pants tucked into white wraps of cloth around his ankles.
Not much is known about Masachika's personality, however, he was likely a very kind person, befriending Sanemi and even introducing him to someone that could help train him. In his will, Masachika considered Sanemi as a brother and wished the best for his loved ones.
After Sanemi began wandering in search of demons to kill, he met Masachika by chance. Masachika was already a member of the Demon Slayer Corps, and he arranged a trainer for Sanemi so he could properly learn how to defeat Demons. The two challenged and successfully defeated the previous Lower Moon One of the Twelve Demon Moons, but Masachika perished in the conflict.
Sanemi rose to the position of Wind Pillar alone, bitter over his friend's death. When he confronts Kagaya Ubuyashiki about the latter's inability to fight, Kagaya apologizes for his weakness and identifies Masachika by name, much to Sanemi's surprise. Kanae Kocho then informs him that Kagaya has memorized every slain Demon Slayer's name and background, and Kagaya decides to give Sanemi Masachika's will.
Sanemi and Masachika had a close brotherly relationship, with Masachika viewing Sanemi as the younger brother he lost.