Naoya Tohara (塔原 直哉 touhara naoya), normally referred only as Naoya (ナオヤ), is a normal human or Maður as they are called in the Álfheimr, he is the father of Asuha and is the first and only member of Rotte's harem (or Rotte's toy from her perspective). He comes from Miðgarðr (the human world). A fateful encounter with Mercelída when he was 12 years old led to Asuha's conception and his eventual encounter with Rotte.
While he is a human, it is later revealed that he is in fact of Incubus descent.
Naoya is a man with blue short hair and blue eyes. He is slim and has a feminine face. While not directly shown, Naoya is extremely well-endowed in his loins. The first time Rotte sees Naoya's penis accidentally, she thinks of a monster and faints, while Kirik thinks of a horse. A similar think happens when he is sequestered by the Marla god cock adoring religious cult lead by Enja, who specifically selected him due to his large phallus. When he is rescued by Rotte, Elíka and Míst, they all see his loins, causing a great effect on Elíka and Míst. Sigurð feels defeated when he sees Naoya's size, commenting that he's like a grade-schooler in Naoya's presence. Even the well-hung futanari Úrsúla has to admit defeat when she catches a glimpse of Naoya's loins.
Naoya is a human from the human realm. At 12 years old, he met Mercelída when she was 18 years old and helped her when she became powerless due to the lack of mana in the human world. In order to return to the human world, she needed to use her succubus ability to extract mana, but no men appeared to be a suitable source except Naoya.
He became an orphan a few years after her first encounter with Mercelída and a little before meeting Asuha. Not much is known of his parents, other than they both eloped from their families to be together, essentially leaving him without any living relative when they both died in an accident. His house is near the park that contain the Yggdrasill tree.
It has been hinted that his body contains so much magical energy which makes him a living breathing magic charger. It is because of him that both Mercelída and Rotte are able to be charged with enough magic to enable them to return to their world. In the manga, it is revealed that this is because he is a direct descendant of the Incubus, one of the ancient races and the male counterpart of the female Succubus that disappeared from Álfheimr eras ago. When Mercelída first found him, she was astonished at the extraordinarily dense mana that Naoya had.
Naoya has an all encompassing love for men and women of all ages, much like Mercelída. Because of this, in chapter 34 of the manga, Ini speculates that Naoya might be a descendant of the Incubus, the male counterpart of the Succubus that is among the extinct ancient races of Álfheimr. Judit originally selected him by using her crystal ball to locate a man who had extraordinary aptitude towards "unusual work" something that hints that he might indeed be an incubus considering also how well-hung he is. This is confirmed in further chapters when, after visiting the Dvergur Miraculous Spring that stimulated her daughter's growth as a succubus, he himself has his incubus traits stimulated to the point of becoming afflicted by the Dream Bondage, a condition exclusive to Incubus that can be treated with Guð Mjólk and only fully cured by a succubus' powers.
Naoya is a very kind and caring individual. He loves and cares for all of the characters in the story even if they bear him an ill will.
Mercelída and Naoya had a deep relationship in the past. Due to the incident that happened to the family of Ygvar she decided to go to the human realm where she accidentally met Naoya. There they shared their past relationship. Naoya was twelve at that time, he was somewhat forced into the sex that they made on that time. That bear their daughter Asuha. Later on it was revealed that Naoya was still angry at Mercelída because it was revealed that the mother of Rotte is also Mercelída.
Naoya loves his daughter very deeply and will do anything to protect her. However, he keeps a secret from her: she (Asuha) and Rotte are half-sisters.
While at first Rotte and Naoya have a tsundere relationship, Rotte warms up to Naoya over the course of the manga and anime, eventually asking him out on a date where Rotte confesses that she is in love with him and Naoya admits that he is in love with her too.