Official Topic Guide: Switch PSN Accounts on Vita

I've been asked a few times as to what the method is for changing back and forth between multiple PSN accounts on one Vita. So here's the (hopefully) simple guide, of which every step should be followed exactly every time.

What you'll need to make this a quick and fairly painless experience;

1. Two memory cards (having only one means either backing up and restoring every time, or deleting everything on your Vita every time - neither are good options)
2. Two PSN accounts and the details to them handy (this isn't a guide on how to make an account in another language...yet)
3. A PlayStation Vita with a charge (or have it plugged in)
4. The ability to read

Here's the steps you'll need to take;

1. With memory card #1 in (I assume this is your default "home" account), open your Trophies application and make sure you sync your trophies by touching the PSN tab and waiting for it to stop loading (the rolling load icon top right stops)
2. Go to the Settings bubble > PlayStation Network > System Activation and go through all three options (which are Game, Video/Music and PlayStation Mobile) choosing deactivate in their internal menus - THIS IS IMPORTANT. See what I wrote just there? Read it again and double check that you did it. Got it? Good. I hope you're sure because forgetting could mean you lose access to things you bought on your account (and will put you through a round-about, extra steps for no reason and annoying process to fix it).
3. Turn your PSVita off and pop out your memory card and any game cards (just in case), then turn it back on (without anything in it)
4. Go back to Settings, but this time go to Format and then Restore This System, accepting any prompts. The Vita will restart.
5. The Vita will turn on like fresh out of the box and you will need to set up a few basic things, just follow the prompts until right after you connect to wifi
6. After connecting to wifi it'll ask you to log in with the account used on the memory card. Log in using the account of this second memory card.
7. An intro video will start which is not supposed to be user-skippable, so instead we'll skip it with the system and plug in memory card #2 (for this secondary account) to force a restart.
8. Activate the system by going to the Settings bubble > PSN > System Activation (it's the 4 Kanji script that's the third down in the Japanese menu) and go through all three options (which are Game, Video/Music and PlayStation Mobile) choosing activate (top answer in Japanese) in their internal menus

To reverse this, simply follow the instructions again.

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If you prefer a video guide, we've got one of those as well;