Rantaro is voiced by Johnny Yong Bosch

Rantaro is a tall young man with light green hair and two small ahoge. His eyes are green and have notably long, thick eyelashes. He wears a dark blue striped sweater with gray pants and slip-on shoes. His sarouel pants tied to his ankles are loosely based on a traditional garb from Islamic culture. His sweater has a big dark symbol resembling his former high school, Hope's Pass High School, as well as both a boat's steering wheel and the setting sun.

When he was first introduced, Rantaro seemed like a mysterious individual. Later it could be seen that he is a carefree and relaxed person, and he is actually described as one of the more ordinary students despite his mysteriousness, with he himself stating that he can sometimes get a bit overwhelmed by the others' stranger personalities. Nevertheless, he is shown to have more patience with some eccentric students like Kokichi and Miu, with a tendency to just laugh off some of things they say. Even though Rantaro cannot remember his talent, he doesn't seem worried about it, instead, he simply looks forward to finding out what it is. He is usually seen smiling and describes himself as "not a suspicious guy". He gives off a really calm and composed vibe and seems like a reliable person. His speech is characterized by being very friendly and colloquial, using the "～っす" copula in his sentence. Fan translations usually adapt this pattern by using teenage slang in his lines. Furthermore, he is stated to have "nonchalant fashionable style" and "serious dedication for looking stylish", and he is a big defender of the idea that your fashion items should express your personality. He has bought clothes from all around the world, though he is also quite picky about his accessories.

Despite his appearance and manner of speech, he has cold, excellent insight, and he is both determined and brave. He even has downright frightening expressions whenever he gets very serious. While the other students descend into confusion and chaos when Monokuma and the Monokuma Kubs state their objective, he is capable of coldly interrogating them about their motives. He also shows a deep understanding of the situation and often talks and acts like he knows something the others don't know,[8] saying profound-sounding and enigmatic sentences, which often make him sound quite suspicious or even eerie. He is shown to be very competent in the Killing Game scenario, understanding that in order to truly win the game you must end the game itself instead of outwitting other participants, and he warns Kaede about her inspirational speeches and strong cooperation with others because it makes her a notable threat in the eyes of the mastermind. During his Free Time Events with Kaede, she notices that he calmly observes other students and makes logical assumptions about them. He plans to end the Killing Game, telling the others not to intervene, but he ultimately fails because of Kaede's actions.