Antonio[]
Antonio was Ophelia's partner and manager for a long time since the beginning of her career.
He was the one who Ophelia wants to sing to, that's why she was working hard enough to sing enough to be recognized. As Antonio didn't see any improvement, He uploaded his own data memory and personality to Ophelia directly, causing his main body to shut down, and Antonio merging with Ophelia. There are times where Antonio emerges within Ophelia, where Diva noticed Ophelia's (under Antonio's control) disappointment after singing.
In the end, Antonio recognized Ophelia's efforts and realizes that Ophelia was singing her heart to be recognized by Antonio, but it was too late, as both of them are destroyed by Matsumoto in the end.
Diva[]
Diva was her longtime idol and inspiration for her singing, and also her older sister.
She was trying her best to become like Diva, who sings with all her heart to make people smile. As she was not confident in her singing, she watches Diva's old video archives and became inspired when she knows that Diva was like her at first, but worked hard enough to be recognized. Diva was also supportive at her as when she was not pouring her heart and confident enough to sing, she talked to her if there was something bothering her and offering advices to help her boost her confidence (though part of it was to analyze if ophelia has suicidal tendencies).
In the end, even if they successfully averted her suicide, they still lament that they still didn't saved her from her destruction in the end.