Kosaka Mamiko is a 1st generation Night St☆r member. She was born on August 21, 1996.
At the beginning of April, she was heard by one of Tsunku's scouts. Tsunku then heard this and wanted to add her to one of the new groups he was creating. After tracking her down and asking her, she agreed to join Hello! Project as a member of Night St☆r.
In the beginning of July she cut her hair.
- Name: Kosaka Mamiko
- Birthday: August 21, 1996 (Age 16)
- Member Color: Violet
- Origin: Kyoto, Japan
- Height: 162 cm
- Blood Type: B
- Looks up to: Oda Sakura
- Western Zodiac: Virgo
- Eastern Zodiac: Rat
- Hobbies: Singing, writing, caligraphy
- Favorite Food: Cherry Cakes
- Disliked Food: Lemon, Celery
- Favorite Flower: Cherry Blossom
- Favorite Subject: Japanese
- Least Favorite Subject: Math
Singles Participated In
- Night Polaris
- Kanashii no Kurai
- Obsessed with everything related to a cherry blossom.
- Is the least mature member.
- Tanaka Aya has remarked that she can be very loud.
- Shares the same last name as Riyu Kosaka but is not related.
- Good friends with Hagiwara Mai, Muramoto Chie.
- Only member not to audition for the group.
- Is good at singing.
- Thinks that Oda Sakura is very cute.
- She is a main singer of the group,