That would certainly help Aqua to track down the man. It's already lucky to get away with a murder (even in Japan with its incompetent police force), but if you do it twice, it's better not to waste time on planning the future anymore. Technically the man didn't murder Ai, and I suppose he wouldn't directly murder Akane either, but with Akane he might need to become more involved. Ai was a bigger celebrity, plus the whole family thing was good fuel. Finding a suitable loser to kill Akane could be more difficult and thus more involved. The windbags attacking her online would be no good.