Saeko Nishiguchi (西口冴子) is a blacksuit part of the team Tonegawa manages in the spin-off series Chuukan Kanriroku Tonegawa.
She helps Tonegawa by giving him her opinion from a female perspective. She is the only female character on the team and possibly the entire blacksuit workforce.
Her Twitter post of latte art depicting the logo of Teiai.
Her Twitter post with a friend.