Ai Kashima

Relationship
Hoshizaki Ren

She is best friend and idol rival of Ren (during their idol days) but she was unaware about Ren's death or having a child (Mahoro).

Mahoro Harukana

Mahoro is Ren's son. She is the second person discovered his secret. Later in series, she become somewhat closer (possibly because their relationship with Ren) to Mahoro. She called Mahoro "Maho-chan" in chapter 31 and 47 . She taking Mahoro's pictures in chapter 49.

Trivia
1. She and Ren are same age and debut as idol from same age

2. There a lot of cactus inside her room.