The idol Kuroki Mio, who had transferred to Usagi's class, has skillfully become acquainted with Usagi. Yet there is a rumor spreading about Usagi's classmates that ""Usagi abandoned Mio and fled"" due to what happened that time that Usagi had to go fight the youma and left Mio on her own in a safe place. Thus, Usagi becomes a lone wolf, because she is not able to tell them that she was actually fighting. [Whoever gets the Kodocha reference wins.]
Making the appearance that she is Usagi's ally- but in actually attempting to ensnare her- Mio is even going to drag Aino Minako into her trap.