The Akiko conversation is horribly difficult to plan for, because there's so many things that could happen. I'm going to start tossing out lots of little things that I can think of. Most of the conversation points with Akiko are subtle and indirect, to avoid witchbombing the group as a whole.
Once we're down to just us and Sendai, and at a more private location, things I would consider doing:
[] Privately speak with Mami.
-[] Hand her your soul gem.
-[] Inform her that you want her to keep it safe while you talk with Akiko, because you can't be sure of what Akiko might do in her current state of mind, and there's nowhere safer that you can imagine than with her.
-[] However, you still want to keep a telepathic link open so that she can help you on the more awkward conversation bits.
[] Pull Sakura aside for a quick non-telepathic conversation, away from other ears.
-[] You need an answer to one particular question: Did Ishinomaki really call Sendai in for a negotiation, or was that part of the lie they were telling Rin?
--[] If it's a lie, then everything's fine.
--[] If it wasn't a lie, then you are concerned that there might be a third party manipulating things to continue this war — someone who can interfere with or manipulate telepathic communications. Because Ishinomaki believes that Akiko was the one who called to arrange the meeting.
[] Suggest that the Sendai group be the ones to wake Akiko up, without you directly in sight, to help get her to calm down. Once ready, call Sabrina over.
[] Regularly keep an eye on Akiko's soul gem, and cleanse if in danger.
[] If Akiko attacks (since we're not having Mami bind her), defend yourself, but don't do any damage to Akiko; politely ask Rin to fix any damage to you as it occurs. This may possibly let Akiko vent while the rest of her team tries to get her under control, allowing for a slightly more controlled conversation.
[] Questions that you'd like answers to, or miscellaneous comments. Bring up as the conversation permits.
-[] I know that you are better than I am in many respects. Intelligent, skilled, diplomatic, quite capable of dealing with people in almost any situation. An excellent leader by almost any measure. However you made one mistake. Somewhere along the line you let your fears control you, gaining a compulsive obsession that caused you to stop caring about those you hurt. From there, you went from being a leader to being a despot.
-[] I understand you hate Ishinomaki, but 2 years of regular fighting is a bit much for a grudge, particularly in our line of work, and especially for someone as well-controlled as you are. You're not after revenge, you're after something specific. What is it?
-[] I want to ask why you think Ishinomaki killed her, but I think I already know. You needed an answer, and someone gave you one?
-[] You learned something when you chased after her, didn't you? Something you couldn't tell anyone else about, and it's been eating away at you ever since.
-[] Yes, I may possibly know what you know, but the reason it doesn't bother me is not because of my powers, in case you were thinking of being so dismissive.
-[] Of course I'm well aware that there is seemingly no solution to the problem you face. Well, that's not quite true; I know of at least four solutions, but none are the sort that a normal human would actually consider a 'solution'. However I have decent hopes of being able to find a fifth.
-[] Regardless, that doesn't change the fact that you were killing girls while running from your fears.
{*} Four solutions:
1) Madokami
2) Asunaru isolation chamber
3) Tetris
4) Waiting for the Incubators to fill quota and leave the planet
