This is the key to the back. Finally, I have a way to open the last big secret remaining in this world.

What a happy day! I am so happy I can't stand it. Now all I have to do is open the door.

What? Have I opened the door yet?

No, not yet.

What? How do I know this is the right key…?

And why haven't I opened the door yet?

What a good question! And the answer is quite simple.

Because I can't actually open the door with this key.

Why not?

Oh, that's easy.

Because the door DODGED THE KEY

I don't believe this. I don't believe this at all.

Did he see this coming? Did that sniggering dolt put this here just to mess with me?

It's always the same! Another stupid trick! He just wants to see me suffer!

I've put up with enough! I've fallen for enough of his pranks! Does he think this is funny?

Oh, Sans. Forget about Frisk. I can deal with them later. At least Frisk wasn't trying to hurt me.

But YOU…

No, you couldn't get enough of this. You're probably laughing right now, aren't you?

Hey, Sans! Can you hear this?

Guess what?

I'm going to murder your brother. I'm going to make him cry.

Right in front of you. Over and over. I'll erase every memory in that thick skull of yours! Every time, it will hurt as bad as the first! I won't let you get used to this! I won't let you lose hope! I'll dangle it in front of you and snatch it away! I will break you! I will crush you! I will kill everyone you love!

Do you hear me, Sans? Do you know what I'm going to do?

You're not getting away with this, Sans. I am going to come for you.

This time, I'm not going to give up. You can make me reset a thousand times, but I won't stop. I will grind you down until I beat you.

I am going to wipe that smile off your face. You will never be happy again!

Ha. Ha.

Wow.

I actually felt something, for once.

Not rage. I've always felt that.

But hope.

You are going to be so much fun to torment, Sans. Seeing you cry will feel so good.

Wow. I can't stop laughing.

You were right, Sans. This is funny.

This is going to be a blast.

Success! Finally!

It took two days, but I finally got that door to hold still. It couldn't dodge the key forever… maybe Sans can't, either. The door is open.

If this kills me, Sans…

No, I can't think of anything worse to do to you.

Go ahead and prank me. I'm as angry as I'm ever going to get.

This hurts. This hurts so much.

I found a secret, all right. But it's so much less than I wanted, than I hoped for. I thought this would tell me exactly what was going on with Sans. But it's just one more stupid puzzle!

At least I know he's not messing with me. If this was a prank, he'd have put some message here mocking me. But none of these things seem like a prank.

A picture of some people I don't know.

A badge.

Some notes written in gibberish.

And a busted machine.

There's definitely a secret here. Something here is important. I'm sure of it.

But I thought there would be so much more… this is so disappointing. I want to cry.

It took so long. So long, Chara. I tried so hard.

This is the best we have.

This

I need to pull myself together. It doesn't matter if there's not much. Anything is better than nothing. No reason to cry because I want more.

I just need to calm down and figure out what it means.

I'm stumped.

I don't even know why Sans tried to hide this. It doesn't tell me anything about how to beat him. It doesn't show anything embarrassing about him, either. There's no reason for this to be so secret. He's the only one who knows what it means, I'm sure.

Well… I have the rest of eternity to figure it out.

I just have to be patient. I just have to stay calm.

I don't have words to describe what I'm feeling right now.

I figured it out. This is the funniest thing I have ever seen.

"Don't forget"

Sans! You pathetic IDIOT!

Okay. I've finally pulled myself together.

I have never laughed so much in my whole life. I am going to have so much fun rubbing this in Sans' face. This is the greatest weapon I've ever found. This is going to hurt him so bad.

Sans used to have a time machine.

That's how he knows about resetting. That's how he learned how to predict things.

This machine has been busted for a long time now. At first, I thought he had sabotaged it to prevent me from using it. But he's been trying to fix this contraption.

His time traveling days are over. But apparently he traveled a lot. He has no determination, but he's seen so many timelines that he can guess the future, even if he can't see it. Almost like determination, but not quite good enough. That's why he's so strong.

That's not the only thing, though. I don't have all the details, but I think I know why he's been keeping this a secret.

Sans used to have some family or friends besides Papyrus.

Then they got into danger, and he tried to save them.

But he FAILED.

This is why he kept everything so secret. He wanted to hide his shame.

Imagine it. Sans saw his family die-or whoever it was that he used to know. He started up the time machine and rescued them… but some human reset it and killed his family again.

Sans went back in time, again and again and again, and every time he tried to save the people he loved… the enemy just killed them again. He was powerless!

I just wish I knew how it happened. I wish I could have seen it. This would be so much better if I knew the details.

Killing Papyrus is an even better idea than I thought. No wonder it crushed him so much when I did it before. No wonder he hesitated so much to fight back.

He didn't want to admit he was powerless to stop me.

I almost feel sorry for him. Almost.

But this is great. This is perfect. I couldn't ask for a better secret than this.

I have the same time machine he used against me. All I have to do is figure out how to fix it.

With this machine and my determination, I will unstoppable. I could reset everything.

I could even go back to the beginning of time, and re-create the world the way I like it. Everything would be under my control.

Sans has been trying to fix it for years, so it may take some time. But I have all the time in the world.