Urenokori no Dorei Elf wo Hirotta node, Musume ni Suru Koto ni Shita

Weiss, witnesses an elf girl being sold into slavery. When he realizes that the girl is not just an elf, but a rare species of elf (High Elf), he decides to buy her and raise her as his daughter. Weiss is at the mercy of raising a child for the first time. Nevertheless, thanks to his efforts, the girl, who was battered and unable to speak, regains her health. Her name is decided to be "Lily," after the first word she spoke. Weiss, who has become a parental figure, is now busy with his goal of getting Lily to attend a magic school! (Source: Dengeki Bunko, translated)