Akuto has brown hair and purple eyes. And notable markings below them. Possibly symbolizing his role as "The Demon King" When his personality changes his eyes become red and the marks under his eyes enlongate and become red as well.
Akuto is seen as very kind. Though once he was told he was the demon king. He persistently tries to justify that he isn't a bad person. It's also seen that he treats women with respect, and often doesn't appreciate constant advances. He also doesn't like being called "The Demon King".
At other times, He has been shown to have a very violent personality with some evil overtones to it. But for good reasons. He sometimes gets into strange situations which portray him as a guy who wants to be the demon king.
Akuto Sai first meets Junko Hattori after helping out Junko's grandmother and Junko thinking he was mugging her. Junko and Akuto seemed to bond over their strong senses of justice. Akuto and Junko enter into a pact a friendship that will end in Akuto's death if broken. Akuto seems to really admire Junko and tells her that he hopes he's in her class.
When Akuto arrives at the school he meets his teacher Mitsuko Tori. When he is examined and given his future occupation he is declared the future Demon King. All of the other students seem very threatened by this and avoid Akuto, (except Ms. Tori who continuously bothers Akuto about killing himself and examining his body.) Akuto ends up being put in Junko's class but the class is afraid of Akuto. Akuto ends up in a duel with Junko and even though he tries to avoid fighitng her, his horrible control of mana causes an explosion of energy. Akuto meets Hiroshi Miwa who starts toi call Akuto "big brother." Hiroshi convinces Akuto to climb Junko's window and attempt to apologize but Junko see's this as an attempt to humiliate her and chases after him. Akuto runs into Kena Soga and she promises to protect him from Junko for personal reasons. Akuto's terrible control of mana causes another horrible explosion and his "observer" Korone appears. Korone brings Akuto to the principal who tells Korone to stay with Akuto so they can be prepared if he actually does become the Demon King.
The following day Akuto meets Fujiko Eto, who tells Akuto that she will help him with anything that he needs. Later, Akuto goes to the bathroom and calls Fujiko and asks her to help him make amends with Junko. Fujiko tells Akuto to meet her in the mountains behind the school, and how to turn off Korone. Akuto runs into a misunderstanding while trying to pull Korone's tail and turn her off, and a demon dog appears. Akuto manages to suck out the demon dogs mana and it turns into a regular dog. The regular dogs starts chasing after Kena who just happened to be following Akuto while wearing a hair pin that turns her invisible. During the commotion Akuto see's Korones tail and manages to pull it, and she turns off. Fujiko appears and suggests that Akuto join the disciplinary committee. Fujiko also gives Akuto a gun and some pills that she says will help Akuto and Junko understand eachother. Kena; whom is still running from the dog, naked, runs into Akuto right as he turns Korone back on. Korone, thinking Akuto has raped Kena threatens to turn him into the school and police, but he convinces Kena to tell her that it was her fault.
Akuto found out about the school's underground after Hiroshi tells him in the school's bathouse, and mentions how Junko Hattori fought down there to gain her popularity. After Hiroshi leaves, Korone asks him a kind of stupid question about sex. Fujiko Eto helps him get an arrangement to meet with Hattori in the underground. When he arrives at the rendezvous point, he is ambushed by a group of thugs who he quickly injures by crushing their bones. When he pins their leader against the wall with his own chain, Hattori arrives, and well, she is convinced he is "betraying her" and when Kena intervenes later, they somehow end up friends again.
Akuto decides that learning to control his power is manditory, and so, agrees to go into the isolation cell, only to be followed by Kena and Korone, when they lock in, Eto appears with intent to cause him to be under her complete control to do with as she pleases. In the chamber they find a map, which Eto gets distracted by and runs off with. Kena photocopies these and posts them everywhere, when students come back injured, Akuto decides to go in and look for the "treasure", Hattori not much further behind. A strange girl named Eiko Teruya follows them and causes problems. Akuto finds out that the labyrinth was once a treasure only the demon king could control and the tasks were set up by the council. Eto takes the key they found and awakens the Dragon Peterhausen, who takes Akuto on, and loses. He swears to live under his command and a picture is taken of the main characters and Peterhausen.