She likes Koshi Nagumo so much that she easily gets worried about him, but would act as if she wasn't worried at all. She has a very heat sensitive body and dislikes being touched.
In the 'After Story' web novel, it is confirmed that Hajime Nagumo marries 8 women after his final battle with Ehit. He ends up marrying Yue, Shea, Tio, Kaori, Aiko, Liliana S. B. Heiligh, Shizuku, and Remia. SPOILERS AHEAD!Jan 21, 2022
Though that is largely coming off them having a sibling-like relationship; keep in mind that Koshi is 12-years-old whereas Atena is around 19 years old a seven-year difference.