
Quick answer — Gou Shinomiya voices Gustav in Attack on Titan Season 3 Part 2, Gabal Docker in Gurren Lagann The Movie: The Lights in the Sky are Stars, Cameron in Princess Principal and 15 more characters.
Gou Shinomiya voices Gustav (Attack on Titan Season 3 Part 2), Gabal Docker (Gurren Lagann The Movie: The Lights in the Sky are Stars), Cameron (Princess Principal), Mao (Jormungand), Shizuru Shirosaki (The Kawai Complex Guide to Manors and Hostel Behavior), Vindalfar (The Faraway Paladin: The Lord of Rust Mountains), Suguru Fuyukai (Inazuma Eleven GO: Chrono Stone), Takahiro Hanaoka (Senpai is an Otokonoko) and 10 more.
Gustav is voiced in Japanese by Gou Shinomiya.