Sena's overprotective and motherly childhood friend and later, the manager of the team.

Mamori's mother met Sena's mother in a cooking class and Mamori and Sena have been friends ever since. Mamori has been protecting Sena from bullies since primary school, to the point that Sena has grown up never having to stand up for himself.

She joined the American Football club to watch over Sena and prevent any bullying by the other members (particularly Hiruma). Despite her joining the American Football club just to protect Sena, she eventually becomes an excellent manager who knows the rules inside and out and makes up strategies for the team.

She is also a member of the school's disciplinary committee.

Source:Wikipedia