Koi wa Deep ni Benkyō‑Chū! (恋はDeepに勉強中！) is a Hulu-original spin-off of Koi wa Deep ni. It shifts focus from the main romance to the third brother, Eitarō Hasuda (played by Watanabe Keisuke), exploring his trials and curiosities about love and relationships. It's a lighthearted, comedic 3‑episode series, diving into Eitarō's humorous attempts at understanding romance—like planning surprise gifts and giving advice to his colleagues.