Seabook Arno  

Kincaido Nau, シーブック・アノー

Seabook was an engineering student from Frontier IV, which is now known as Side 4. He may have been a Newtype, although this has not been confirmed. His mother, Monica Arno, left the family to focus on her research in mobile suits like the F91 Gundam. This led to resentment towards her from Seabook. Through a series of events, he piloted the F91 to protect his friends and save Cecily.