the god of thunder and the demon king.Kanji is granted the power of two personae throughout the game: Take Mikazuchi and its "evolved" form, Rokuten Maou.
Many of the personae which the investigation team inherit look back to Japanese mythology and folklore, particularly those that tie in with Izanagi. He is the protagonist's persona and the Japanese creation deity, who together with Izanami created the islands and gods of Japan. According to legend, when the fire god Kagutsuchi was born he burned and brought upon the death of his mother Izanami (thus marking the end of the creation, and the beginning of death.) In his grief Izanagi beheaded him with his sword, and the blood that adhered to the sword brought birth to Take Mikazuchi along with a number of other deities. Take-Mikazuchi is born from this situation as if his birth counteracts the death that had been brought about, similar to the role of Kanji and the rest of the investigation team. He is the god of thunder, hence his abilities to use Zio attacks, and is also said to be the founder of ancient sumo wrestling: perhaps an interesting tie-up for Kanji, who's the strongest on the team in terms of physical attacks and is also pretty well known for beating up biker gangs in his free time.
Interestingly enough, many of the other initial party members personae are also directly related to Izanagi: Yosuke's Susano-o and Yukiko's Amaterasu are considered one of Izanagi's "three noble children": these party members are the few who begin the investigation team, as well as rescue and recruit a number of other members, similar to the way Izanagi and his children bring life to the deities and elements of Japan.
Kanji's evolved persona, Rokuten Maou is known as the Demon King of the Sixth Heaven. In Japanese Buddhism he symbolizes the lust for power, and with a large number of minions at his beck and call, is known for disturbing the practice of dharma and tempting Buddhists from practicing the teachings of Buddhism. Rokuten Maou is a persona inherited by Kanji after accepting his true self: the self that is not afraid to show the world who he really is inside, despite the fact that these may not be the "accepted norms". Rokuten Maou is a symbol of power and rebellion against the laws set before him. Similarly, Kanji searches from strength within him so that he has the courage to be his true self: he goes against the grain and strays from the "rules" regarding gender and sexuality, which the society around him has created.
Persona DesignKanji's personae are of the thunder element, and their overall figure is similar to that of a giant robot, echoing the traits of Kanji's imposing figure as well as his association with electricity (Take Mikazuchi even features what looks like electrical cords in his arms). Take-Mikazuchi wields a giant thunderbolt as if it was a sword, securing his place in the team as the god of thunder. He may as well carry it to reference the mythological figure he represents, paying homage to his sword Futsunomitama. Take-Mikazuchi features a skeletal design on his body, most likely to reference the skeleton featured on the shirt Kanji wears under his Yasogami High uniform. After all, it wouldn't be too unusual for his personae to take on an aesthetic appearance like Kanji's since we can assume that he's quite fashion-conscious.
Kanji in his winter and summer wear, which are styled similarly to his personas.
Rokuten Maou is an unusual opposition to his first form as his body features flames--strange for a persona whose element is thunder. However, by taking a look at some of the original sketches it becomes fairly clear that the overall shape of the head references a samurai helmet, particulary with the crescent shape that mimicks the front crest of adorned kabuto. With the name Rokuten Maou, it's possible that the artist is referencing the 16th century shogun, Oda Nobunaga, who was sometimes referred to as Dairokuten Maou for his cruel misdeeds. The flames may in fact reference Oda Nobunaga's death: after comitting suicide, it was said that his page set Honno-ji on fire so that no one would be able to take his head as a war prize. That being said, Kanji also wears a shirt with a flaming skull on it during the summer: like Take Mikazuchi, Rokuten Maou may very well just be taking from Kanji's clothing designs as well. (It's really kind of that chicken and the egg thing, no?)