Lukka Austri (リュッカ・エイストリ), mainly called by her first name only Lukka, alternatively Lucca, is a Dvergur (dwarf) and the princess of the North Dvergur country (北ドヴェルグ国). She attends the same school as Míst, Yuna, Rotte and Asuha, all of whom are her friends.
Like all Dvergur, Lukka is of small height. She looks younger than Rotte and Asuha despite being older than them. Her eyes and hair are brown towards a chestnut variation in both the manga and the anime. Occasionally she wears bunches, but mostly has her hair free. She is not used to wear underwear since she doesn't do it in her hometown.
Lukka is an exchange student from the Kingdom of North Dvergur, of which she is the princess and the daughter of Holti. During her stay in the Kingdom of Ygvar, she freeloads at Yuna's household. Yuna's mother also provides Lukka with cute clothes that a young Yuna used in the past. Contrary to her small body frame, she is a big eater.
Later, in advanced chapters of the story, her father suggests that Naoya marries Lukka, as he is impressed with Naoya's character and virtues, but Lukka quickly tells him that Naoya is Rotte's.
Her personality is very easygoing. Being from a different country, Lukka doesn't have the same constraining parameters as the people of Ygvar. As such, her sense of modesty is quite different, being closer to Asuha's. Because of this, Lukka and Asuha get along pretty well and are often ignorant off why the others are embarrassed or uncomfortable in certain situations. Like Asuha, she'd rather not wear panties. When her father suggests that Naoya marries her, Lukka declines as Naoya is Rotte's and it doesn't get clarified whether or not she has a romantic interest in Naoya, although her interactions with him seem to suggest that she doesn't.