As Hiroko's boyfriend and Ayato's friend, he was always close by, but as a Mulian, his real purpose was to monitor Ayato.
In Depth[]
Mamoru Torigai is another friend and classmate of Kamina's in Tokyo Jupiter. He was seeing Hiroko Asahina before she left Tokyo Jupiter with Ayato. Deep down, he dislikes Ayato because of Asahina's feelings for him. Mamoru is a true Mulian, like Ernst von Bähbem, Maya, and Quon, and holds a high position within the Mulian society. He follows Ayato to Nirai Kanai the second time he leaves Tokyo Jupiter and lives with Ayato for a short period of time. While in Nirai Kanai, Mamoru discovers that Asahina died. He blames Ayato for her death and fights the RahXephon with his Dolem Obbligato. His Dolem is no match for the RahXephon and loses an arm in the battle. He returns with a fully repaired Dolem and battles the RahXephon again, this time after Ayato had joined with the RahXephon, and dies in the battle. He is brought back to life, along with Asahina, when Ayato re-tunes the world.
His given name, "Mamoru," also means "to protect" in Japanese. In the light of his failure to protect Asahina and his turning against Ayato, his name becomes ironic.
In other versions[]
In the movie, Mamoru's role is similar to that in the TV series.
In the manga, Mamoru only appears as a classmate who makes unsuccessful advances towards Asahina.