Quick answer — Nikki Asada worked on Sound! Euphonium 3 (Original Character Design), Sound! Euphonium 2 (Original Character Design), Sound! Euphonium (Original Character Design) and 7 more anime.
Nikki Asada worked on Sound! Euphonium 3 (Original Character Design), Sound! Euphonium 2 (Original Character Design), Sound! Euphonium (Original Character Design), Tokubetsu-hen Hibike! Euphonium: Ensemble Contest (Original Character Design), Sound! Euphonium The Movie — May the melody reach you! — (Original Character Design), Sound! Euphonium: The Movie - Our Promise: A Brand New Day (Original Character Design), Sound! Euphonium: Ready, Set, Monaka (Original Character Design), Sound! Euphonium The Movie: Welcome to the Kitauji High School Concert Band (Original Character Design) and 2 more.