Arata Kangatari

In a mythical world where humans and gods co-exist, a ceremony marking the new governing princess is about to occur for the first time in 60 years. Only a girl from the Hime Clan may take this position, but the lack of females born to this family means that a boy called Arata must pose for the role. During the ceremony, the Twelve Shinsho, the wielders of special swords called Hayagami, led by Kannagi, betray the princess by trying to kill her and Arata. Arata escapes and runs into the Kando Forest. He emerges from the forest and finds himself in the alley in present day Japan. He has a run-in with the police because he is shirtless but is saved by Nao, a girl who claims to be his sister.
Meanwhile in modern-day Japan, a boy named Arata Hinohara is starting his new life in high school. He wants to put memories of his difficult past behind him, but things aren’t going to be simple when Kadowaki, the bully from his old school, emerges. Kadowaki's bullying continues, and Hinohara discovers that his friend, Suguru, allied with Kadowaki and covered his desk with glue. Feeling angry and betrayed, he walks into an alley, and soon finds that is no longer in Japan, but rather a new world, Amawakuni, the other Arata's home. He is helped by Arata's grandmother and Kotoha, Arata's childhood friend. When Kannagi searches their house, Hinohara comes across a rusted sword and activates its power and becomes a sho. The sword is a Hayagami, or god, named Tsukuyo.
Kotoha gives Hinohara a stone (michihi no tama). He is arrested, and in a jail cell, talks to Arata through the stone. He discovers the truth behind the princess' assassination, and both realize that they are in each other's worlds and being mistaken for each other. Hinohara is speedily tried, found guilty, and exiled to Gatoya Island, a place compared to a living hell. On the trip to the island Kotoha tags along and gives him his Hayagami. Also because of the stones power he is able to talk to the princess (who is just barely alive) and she asks him to govern the world as otherwise there will only be war and bloodshed.
On the Gatoya, he meets two friends, Kanate and Ginchi, who try to steal his belongings and Kotoha. Kotoha soon disappears, and Hinohara, desperate to find her, trades everyday items from Japan for information. He discovers that Tsutuga, the warden of Gatoya Island, is a sho, and confronts him. Hinohara learns that Tsutuga was betrayed and empathizes with him. Tsutsuga decides to give his Hayagami to Hinohara, and becomes one with his Hayagami. Hinohara uses his new power to then restore the island. He and Kotoha escape with their new friends, Kanate and Ginchi, to the mainland to restore order and save the princess.

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Main characters
Arata Hinohara

He is one of the main characters of story, along with Arata. He was an ordinary troubled teenager pulled through another dimension to the world of Amawakuni where he is put into a contest to become the world's emperor.
Hinohara begins as a shy, tortured soul who is continuously bullied throughout his early teenage years by his ex-best friend Masato Kadowaki.
Hinohara's time in the new world helps him grow as a person as he begins to find himself and put trust in others. He grows stronger and after years of being bullied, strongly refuses to let the Twelve Shinshou treat ordinary citizens in a similar manner. His character change can be credited partly to Kotoha who teaches Hinohara that he should love himself and how his life does have meaning-protecting those who can't protect themselves. Hinohara has a sense of humor that is shown throughout fragments of the story.

Arata
He is a Himezoku
member whom was labeled as a female in the government by Makari in order to prevent him from getting eliminated. Despite we don't get many scenes of him, regardless he's still one of the main character, along with Arata Hinohara.
Arata is very brash in his actions, and refuses to let others bully him. Arata has good fighting skills and uses these skills to help allies. Arata doesn't have an easy time of focusing and is easily confused. The modern world and terms still confuse Arata who doesn't understand the technologies and slangs.
Just like Hinohara, Arata has a strong sense of justice and determination, and refuses to stand by as an observer when people harm an innocent.
Arata is also shown to be oblivious when it comes to feelings and people's sarcasm. He's also very goofy and is only annoyed by his grandmother's determination to make him pretend to be a woman to become Himeou's successor. Upon the attack on Himeou and the Shinshou's betrayal he swears to save her.

Masato Kadowaki

He is one of the main character in the series. He is the former childhood friend and now bully of Arata Hinohara. He had a intense hatred toward Hinohara since middle school, therefore he plays the major antagonist in the series.
Kadowaki is a complicated young man. He started off as a kind adolescent only interested in sports, where his favorite event was running track. However, his personality grows sour during middle school when his mother abandons him and his influential father begins adulterous affairs. All this chaos builds anger within Kadowaki and through his stubborn pride he refuses to accept the abandonment. He grows jealous of Hinohara who is well-liked for his personality and not through his family's financial affairs. Kadowaki begins bullying his best friend as a means to satisfy his own loneliness and bitterness.

Kotoha

She can use her healing ability to heal people in Arata's group.
Kotoha is overly bubbly and wishes to help others. She is a magic user and likes to use her abilities to treat injured teammates. Kotoha is the type to put others before herself and will endure physical harm trying to save someone. Kotoha has been in love with her friend Arata since childhood. However, her feelings are starting to shift towards Hinohara who reciprocates her affections. Kotoha doesn't like for others to belittle themselves as she believes everyone is special in their own way.