For anyone that is wondering why Sara and Elena allowed Akira to do something dangerous:
Their pay is based on the number of survivors in the main unit. I'm assuming that Akira knows about this too, so they won't get paid if the main unit is wiped out.
I'm guessing that Sara and Elena thought...
That AI is in such a rough spot that she needs to use another AI's host to save her host. This is the sort of human stupidity that creates a Skynet or Durandal.
Also, did Yumina not get affected by Katsuya?