Ruby's past life was Sarina Tendoji. She was a patient in a hospital. Apparently, she was sick since childhood. She had no hair due to chemotherapy. At the age of 12, she died of anaplastic astrocytoma.

But that wasn't the end for her, as she was reborn as the child of her favorite idol, Hoshino Ai. She has a twin brother who is also living for the second time. Ruby loves her mother and brother with all her heart.

At the age of three, Ruby was able to overcome her fear and began to show signs of becoming an idol.

Ruby continued to train to become an idol. She first auditioned at the age of 14, but was rejected because she was considered too young. She auditioned again 2 years later, when she was 16. Although this time she failed again, it was only because of her brother.

Eventually. Ruby becomes a trainee at Strawberry, the agency that Ai's group was formerly under. The second member of the group is Arima Kana, a former genius child actor, and soon Mem-cho joins them. After some deliberation, Ruby decides to name her group B-Komachi.

Ruby is very impulsive and cheerful. She is a vulnerable, but at the same time very goal-oriented person. She kept her mother's promise that she would follow in her footsteps and become the greatest idol.

Ruby is a short, beautiful, and slender girl with pale skin. She has large pink eyes that resemble a stone called ruby. Her left eye has a six-sided star, while her right eye is missing one. The girl also has golden hair that reaches her back.