Nami Ootake

About

Nami is Yumi's twin sister. She is single, not a mother, and more adventurous. She moves in with her sister to help take care of the new baby, Yumi's nephew.
Unlike her sister, Nami wears more provocative underwear.

In the past; Nami used to sleep around a lot with seniors in her club, school teachers, coworkers at part-time jobs, kids that she was tutoring, and a lot of junior (rookies) staff at the work place. She has lost count of how many people she has slept with.
She has also been with Yumi's husband before they were together.
Her first time was with a senior year of middle school but she started having it more regularly in highschool

She is the first one to have sex with Shinji Kanou (however Shinji thinks this is Yumi since they met each other near her apartment complex). Nami eventually convinces Yumi in becoming sex-friends with Shinji and herself.