She is Sena’s childhood friend who is one year senior to him. She is overprotective about Sena, as she joined the football club as a manager just to make sure he would not be bullied by his teammates, especially Hiruma. Being one of the brightest students in the school, although she did not know anything about the American football prior to joining the Devil Bats, she learned the entire rule over night, and eventually became the brain of the team, along with Hiruma. However, she does not know that “Eyeshield 21” actually is Sena just yet.
Mamori is Sena’s childhood friend and is also a year older than him. She is very overprotective when it comes to Sena, and joins the football team as manager so she can keep an eye on him and make sure the other players—especially Hiruma—don’t bully him. She does not yet know that “Eyeshield 21” is actually Sena.