Sigurð Sveinnsson Svarthæð (シグルド・スヴェインソン・スヴァルトヘイズ), mostly referred by his first name Sigurð or the alternative spelling Sigurd, is a Nótt Álfur and a prince of the country of Svarthæð. He is one of the main support characters through the series, mainly in the manga.
A hot-headed guy who likes women a lot, Sigurð for some reason falls in true love with Rotte despite her not being the type of woman that he normally looks for. For this reason, he considers Naoya his rival. His sister Helga and his assigned guard Dóra have to keep watching over him at all times to try to control the impulsive prince. While his father, King Sveinn worries about him, he actually trusts in Sigurð more than his other son and Sigurð's older brother Rúrik despite the later being older and more mature.
Sigurð is tall young man with unkempt gray hair. He mostly keeps an untidy appearance, wearing regularly his school uniform without a shirt and with the jacket unbuttoned. Like all Nótt Álfur, his skin is brown. He has a noticeable scar on his nose.
Sigurð is the second prince of the Kingdom of Svarthæð and the son of King Sveinn. He has three siblings: his older brother Rúrik, his older sister Helga and his younger half-sister Críe. All his life he was trained to be a soldier, but King Sveinn managed to achieve peace in the Kingdom before Sigurð was ever deployed. Sveinn decides to send Sigurð to study abroad.
During his stay at the boys school, he meets trouble makers Bjarki and Kató, kindred spirits that lust for women, although he normally ends up just using them for what he needs at the moment and some times leaves them unconscious.
After Rotte rejects him, Sigurð decides to travel abroad. During his travels he encounters many women from other cultures, and at one point a woman fell in love with him and it was only thanks to Dóra's intervention that nothing developed. He eventually returns to duel with Naoya and clear his remaining regrets. Sigurð is unable to get the upper hand despite Naoya not using his grappling skills. They are interrupted by a band of thieves that are looking for Naoya and have Dóra hostage. As Sigurð appears to leave Naoya alone to deal with the bandits, he instructs Dóra to distract the guy that's hlding her and Sigurð immediately attacks the thief. With that distraction, Naoya quickly subdues the other thieves. As Sigurð thinks they still have to deal with the lingering bandits outside the warehouse where they are, he finds that they all have been dealt with thanks to Naoya's previous preparation with Zelda prior to arriving to the duel, showing him that Naoya is not as naive as he thought. After some more bonding, where Sigurð feels like a grade schooler next to Naoya's loins, Sigurð acknowledges Naoya and Naoya also reveals that during their fight, he didn't go all the way not because he was naive, but because he likes Sigurð.
When his brother Rúrik attempted to mount conflict by setting a coup attempt against Mercelída's regime and poisoning his father to become the leader, his plan fails as the coup is stopped and Sveinn was already prepared for such a thing and had assigned the military command to Sigurð, who comes through and stops his brother.
Sigurð works as the leader of the Kingdom for a short time, but quits as soon as he find out that his father survived, despite his father's wishes to leave him as the leader of the country.
Sigurð is a womanizer that normally enjoys women with big breasts. He likes to drink and enjoys brawls. He is a hotheaded and normally punches before asking. His wild and free spirit is completely opposite to his brother's. He always tries to peep on women when there is a chance. Dóra is always close to him to try to stop him whenever problems arise, which is almost always.
When he first encounters Rotte, he falls in love at first sight and claims that this is different from what he has felt for other women. This seems to be true as his attitude towards her is unlike any other shown towards other females in the story. Sigurð also cares for Dóra, although he doesn't seem to notice that she has feelings for him. When Dóra injured her eye in an incident caused by him, he gave her an eyepatch that she keeps wearing even when hey eye is no longer injured because she treasures the gift that Sigurð gave her.
Despite his nature, his father trusts him completely, to the point of appointing Sigurð as the leader in case something happened to him. Sigurð comes through as a capable leader when a crisis caused by Rúrik occurs. Despite this, he doesn't like the idea of being the king of Svarthæð.