Armin is considered a genius by his peers, and he can be very serious at times. He is typically very relaxed, and he is a very kind and understanding person. Armin has Hanahaki, a disease in which the victim coughs up flower petals when they suffer from one-sided love. It ends when the beloved returns their feelings (romantic love only; strong friendship is not enough), or when the victim dies. The victim will cough up petals, and when close to death they will cough up full flowers.