Rei Ryugazaki is a main character in the anime series Free! He is a member of the Iwatobi High School Swim Club and is known for his analytical approach to swimming. Initially a member of the track team, Rei is persuaded to join the swim club due to his admiration of fellow member Nagisa Hazuki. Despite his initial struggle with swimming, Rei becomes proficient in the butterfly stroke. His character is intelligent, with a penchant for mathematics and logic, often wearing glasses as a symbol of his studious nature. Rei brings a unique dynamic to the swim team with his dedication and determination.