The Rising of the Shield Hero Volume 25: The Manga Companion

"I want to become a shield for the Shield Hero "
Naofumi finds two siblings of the rare demi-human race known as the hakuko, Fohl and Atla. The brother, Fohl, fought in the Coliseum to earn money to save his sister from a devastating disease. Naofumi decides to use the Elixir of Yggdrasil for the sister, Atla, but only if Fohl gives him fair compensation.