Masato is a wealthy demon from Hell and a recurring antagonist in the anime RIN-NE, including its third season. He has short purple hair, purple eyes, bat-shaped markings on his cheeks, and bat wings, and he typically wears a tuxedo. His name roughly translates to an evil, narrow-minded person, which reflects his personality. He is cruel, petty, and holds relentless grudges, showing no pity even for women and children. Despite his wealth and possession of powerful and wicked techniques, he is surprisingly weak in direct confrontations and is frequently defeated by Rinne Rokudo and Tsubasa Jumonji. His intelligence is somewhat lacking; he is a poor speller, and his carefully laid traps are often childish and easily backfire.

Masato’s primary motivation stems from a childhood grudge against Rinne that began during their time at Demon Elementary School. When both were assigned to retrieve an unsalvageable soul—a dying rabbit—Rinne revived the animal by feeding it, ruining Masato’s task and causing him to fail. This incident led to a lasting enmity, and Masato constantly seeks revenge against Rinne. He collects souls for Hell and wields the power of fire, though his abilities are often outmatched in direct battle. In the story, he serves as a minor antagonist who repeatedly attempts to thwart Rinne’s shinigami duties, often with comedic results.

Key relationships include his rivalry with Rinne, his frequent defeats at the hands of Tsubasa, and a secret crush on Sakura Mamiya, whom he sometimes tries to impress. He is also jealous of Rinne’s connection to Sakura. Over the course of the series, Masato shows minimal growth, remaining largely defined by his petty grudges and repeated failures. He appears across all three seasons, consistently playing the role of a wealthy but incompetent demon whose schemes backfire. His notable abilities include flight via his bat wings, fire-based attacks, and various demonic techniques, though he rarely succeeds in using them effectively against the main characters.