A high school student of Kuyo High School who suffers from insomnia. He comes off as grumpy and unfriendly due to his condition. Ganta is determined to protect the observatory and the revived Astronomy Club, of which he becomes the president.
After meeting Isaki, he opens up to the people around him and reveals to Isaki that the cause of his insomnia is due to separation anxiety caused by his mother leaving him and his father.
He becomes Isaki's boyfriend at the end of the club trip during the summer holiday of their first year. He aims to get into a university with a nursing program in Kanazawa, Ishikawa, inspired by his desire to always be at Isaki's side.
