Let me relate the story of my J-Pop Idol character. ...
Here is what I came up with, using your story as jumping board.
So a Renraku exac made a deal with the J-pop idol is secret, to work for Renraku after she hits 18. The deal is she would write songs and later even perform (after some minor facial plastic surgery, all them idols look alike). Along the deal the exac threatened the idol, they would kill her adopted brother (the player), manager and anyone she hold dear. So she reluctantly agreed.
All this is due to the binding nature with the manager, they would use a Bunraku doll to substitute her until her contract is up with the manager. While the idol emerges as another super idol in the hands of the Renraku exac.
At the the idols 18th b-day party/concert a group of 4 shadowrunners + 1 otaku (not the hacker kind), *poof* in and make a scene declaring "You scum, calling your self fans of [idol name], *spits*. We the loyal fans of [idols name] will not be tricked by lowly imitations such as this one. THE IDOL YOU WORSHIP IS A FAKE!" (or something like that). Then *poof* they disappear. (The use the stage, and the trap doors to get in and out (old school tricks)).
- The thing that nobody know is that the otakus somehow found out about the deal between the Renraku exac and the Idol. The problem is they are missing some details, like the switch has not happened yet.
On their way out the Idol's (Russian) bodyguards (probably ex-special forces (cause all Russians are ex-special forces.

)), lead by the managers sister, intercept the kidnappers but they get away (this might enforce the idea that these are shadowrunners, a possible lead).
While the players and the Knight Errant are dealing with the after math the kidnappers get to their hideout and wait till the Idol wakes up. They will try to get a confession out of her on camera.
The Renraku exac isn't happy that his asset has just been stolen. He pulls some strings (or maybe has the authority) to call in a Renraku search-and-rescue team.
At this phase the story will depend on what the players want to do. If the do their own search and rescue, then its a normal run, where they will run into the Renraku team, all to the joy of one of my players. The idol might tell the player (adopted brother) about what she had done, and then move on to the next part where the group tries to find the exac, break the contract and so forth.
If they opt to leave all of it to the Knight Errant, then all of this happens in the background, the Renraku team saves the idol, using the opportunity to make the switch. Then the Bunraku doll will blame most of her "off beat" actions on the traumatic ordeal. Maybe at some point the manager will talk to the player, "does something seems off" or "you go talk to her", or something, giving the players a lead.
Thanks for the story CitizenJoe, it gave me this (IMO, great) story idea.