It's Aria's arc. Wild theory but I think Michiru is planted by Otoboshi pres to test his children and see who can succeed him.
same, In the story, we see Aria's brother displaying arrogance as he is willing to resort to cheating twice during a match. He tries, but fails, to give Michiru premade song and dance for the group even though she is working with him. Unlike his sister Aria, who takes the time to understand the idols' personalities, he struggles to connect with them. Aria, on the other hand, has a keen ability to recognize talent. Despite any setbacks, she encourages the idols not to give up, believing that if they have the talent to perform on stage, they also have the potential to succeed in life if they stay committed. Interestingly, it seems Aria may be unaware that the auditions are being rigged, or if she does know, it hasn't been revealed yet. She appears genuinely invested in the auditions, wanting the girls to showcase their talents so they can shine as stars. This suggests that she is a remarkable idol herself, yet she is eager to uplift other girls to become great performers too, which indicates she doesn't mind if her spotlight is shared. Although her expression can be smug, the final panel with her father shows a more serious and nervous side, in contrast to her brother, who continues to smile with pride and arrogance.