"The world just doesn't want to stay saved." Jaheira, Baldur's Gate 3. Fits Serenais very well.
Have you seen Blue Eye Samurai? I am not sure how it compares to Dungeon Meshi or Frieren (I haven't seen them yet), but personal opinion is that Blue Eye Samurai is surprisingly good.
The choice stuck, and she has worn black ever since, with very few exceptions.
Serenais wears black. I personaly think it is a good contrast to her white hair and pale duskwight complexion. Headcanonwise, she herself chose it, when she moved to Sharlayan; everyone at the Studium wore mostly white. The dress code, however, didn't specify color. So, she wore black.
(...) There, Serenais' parents made sure she had a happy childhood, but also a good education. When she grew up, Serenais was bound to be conscripted into Ishgardian military, but with the support of her parents, and visiting scholars, she was able to flee to Sharlayan.
(...) But Serenais' parents made it, and were allowed to settle in the Brume. That is where, two years later, Serenais was born. Not long later, Serenais' father found work in Jeweled Crozier as a blacksmith, and they were allowed to move there. Luck finally found the family. (...)
(...) For that, she and Sonat were treated extremely badly. Just two months later, Sonat died, and Serenais' mother almost died with him. It was then when Serenais' parents decided to flee further, to Ishgard. It wasn't without peril - many refugees didn't survive the route. (...)
(...) Only at Ul'dah they were accepted. It wasn't good, though, either; the Monetarists treated the refugees little better than slaves, and often kidnapped and sold them as such. Serenais' mother gave birth to Sonat, a boy, at that time. That meant she wasn't able to work. (...)
Serenais is a daughter of refugees; her parents fled from the advancing Garlean empire. They fled through Ala Mhigo, where they were rejected; the locals feared refugees might be garlean spies and saboteurs. They went by Gridania, where they were rejected for being Duskwights. (...)