You cave and agree to Hiyoko's demands.

The threat of **** is too much, and you quickly give in to Hiyoko's demands. You might have some other device to subdue Hiyoko by ****, but using your hypnotism recklessly is what got you into this mess. You won't let yourself mess up another person the way you messed up Mahiru.

So, you tell Hiyoko the truth. You aren't sure if there's a quick way to fix Mahiru-

Ouch! The grip tightens. You hurry this along. You tell Hiyoko the reason it won't be fast is that you don't know Mahiru well. If you knew her, maybe you could put pieces together to reconstruct her personality without having to try a million times.

"Haaah? Is that all?" Hiyoko gives you a disgusted look. "Use that engorged nerd brain of yours! Big Sis Mahiru is... my best friend," she declares, blushing a bit as she does. "There's no one in this school better equipped to tell you what kind of person Mahiru is. So, the three of us are gonna ditch morning classes, you're gonna sit your fat ass at your stupid nerd bench, and I'm gonna go over every detail of her great, normal personality. Then, you're gonna work your black magic, only this time, you'll use it to fix her instead of fuck her up. In return, I won't tell anyone about how you messed her up in the first place. Deal? Deal."

... It's a deal. You tell Hiyoko, though, that this won't be a fast process, and that even with her help, there's no guarantee of success. At best, this might only restore Mahiru to the type of person Hiyoko thought she was before. After all, it's not like a best friend knows every detail of their best friend's life. The chances of restoring everything that made Mahiru one-hundred-percent "Mahiru" are impossibly slim.

"It's a little early for quitter talk, don'tcha think?" Hiyoko tells you with a smile that's not at all comforting. "Now, we're gonna start from the veeery first moment Mahiru talked to me, then work our way through the time she helped me learn to tie my own kimono, then all of the classes we took together. Oh, and we have to talk about her photography! Photography is like everything to Mahiru, so we've gotta restore that."

At some point, this party had drifted into your room and the door had been shut. Probably for the best that anyone who happened to be awake didn't overhear you talking about rebuilding their classmate's brain. The woman of the hour herself was seated on a stool by your workbench, squirming uncomfortably with the headphones on her head. "Mahiwu feels like you're ignoring her! Idiot Tomo, hmph!"

You are paying complete attention to Mahiru through the stories about her, while simultaneously paying no attention at all to what the broken version says. You're faced with the task of restoring the brain, personality, and even talent of an Ultimate. Success seems impossible. The good news is Hiyoko appears more willing to talk now and less interested in killing you. The bad news is she does expect your complete devotion to this restoration project. You find yourself splitting your focus, putting half of it on Hiyoko's doting and comprehensive description of her friend and half on how you might expedite the process.

For instance, you originally suspected Mahiru had lost her photography talent from your brainwashing... However, you hadn't specifically put in some trait like "has no skill in photography." It isn't a confirmed negative, just a lack of a positive. Maybe there's a way to restore her talent after all?

Hiyoko snaps her fingers loudly in front of your face. "Are you listening, dummy?! I'm telling you, the thing that's really great about Mahiru is-"

You tell her you've heard enough. Now that you've had a breakthrough, together with what Hiyoko has already shared, you're confident you can restore Mahiru's personality just like she wants it. You want to get to work on it ASAP, so you don't end up missing a bunch of classes. You add that there's no reason she has to stick around... In fact, you'll work faster without the added pressure.

"No way! How do I know you won't add something screwy to Mahiru while I'm not watching?!"

You tell her that, frankly, she won't know even if she is watching. One movement of the solder on the circuit board of your chip probably looks the same as another to her. You promise her, though, that there are only two intentional changes you'll make from what she told you and what you're able to recover:

First, you'll make it so she doesn't resist or resent the idea of being brainwashed, either in the past or in the present. You can tell Hiyoko is bristling at that idea, but you remind her that the reason is if she knows she's being brainwashed, she might resist further brainwashing. This might not be a one-time thing, depending on your success, so you need to make it so Mahiru buys into brainwashing while she's still compliant enough.

Second, you'll make it so she has a switch one can activate at any time that sends her into a "sleep mode," making her easier to control while the two of you fix her. A keyword that the two of you would never say by accident... You decide to make it "Mahiwuwuwu."

The blonde frowns, crosses her arms, then sighs. "What a pain... I don't trust you at all, but I'm not dumb. I get it. All right, just do your thing. You said you can do this fast, right? By lunch time, you better bring me a fixed Mahiru! No funny business. Remember I can blow the lid on your freaky Frankenstein lab here any time I want, okaaay?"

You nod, then shoo her off. This will be the most complicated project you've ever done, on the tightest time budget.

Mahiru speaks up from her sitting place again, having removed the headphones from her ears so she can join the conversation. "Yeah, buzz off, Hiwoko! Me and Tomo need a little private time together in her room... N-not so Mahiwu can be alone with Tomo and do anything dirty, not like that! We just don't want you here, hmph!"

... You ask if you have permission to install the shutoff switch early, and Hiyoko quickly agrees. She has no desire to see her friend like this, either, so she gives you one more threat for good measure, then leaves. Now, you can get to work...

You do so, trying to ignore all the classes you're missing. You do think you can restore most of Mahiru's personality, just as it was. You can't freely sort through it and alter it that way, but all you really have to do is work backwards through the artificial prompts you'd given her earlier, and it ought to work as a system reboot.

But, you find yourself wondering... Is that really what Hiyoko wants? You think back to her glowing description of Mahiru, and remember her threat to tell everyone about what you've done... If there's any flaw in Mahiru's original personality, would Hiyoko blame you for it and blow the whistle? You might have to think outside the box here, in order to save your skin.

You could try for the full, perfect restore. When you boot Mahiru up, you ought to know quickly if it worked, and Hiyoko would have no reason to complain so long as it's successful. However, it'll be delicate work. What if it only seems perfect, then falls apart in a way you can't predict when the two of them interact? Or what if it actually is perfect, but Mahiru behaves in a realistic way that isn't what Hiyoko expects?

Alternatively, you could focus less on a full restore of the original and more on giving the client what she wants. The Mahiru that Hiyoko described... If Hiyoko likes it more than the actual Mahiru, what could she have to complain about?