Part 52
Completing the game on Hard difficulty unlocks this bonus stage.
095 +07:00 Shibito ------- Primary --- VIDDLER / GAMEVEE
Getting archive 079 (the AGE MANIAC game machine) also unlocks a minigame that can be played from the Top Menu.
It's not at all fun and a pain in the ass to play, but check out the video for a demonstration.
Kunitorisu (link not mine)
YouTube
Finally, once completed on any difficulty setting, any stage can be played through on Time Trial mode. The only difference from a regular run is the clock in the corner of the screen like in Kyoya's stage (only this one is counting up, not down). There are no pre-set "High Scores" and no tangible reward for completing stages in this way.
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And that's it for SIREN 2. All 100 archives have been collected, all minigames unlocked, and all stages completed on the hardest difficulty. Nonetheless, if you can tell me you have a complete and perfect understanding of everything that happened you're probably lying. So this is your chance to ask questions about the events of SIREN 2. I'll do my best to answer anything you're curious about and to find out the answers to the things I don't know. Like most games these days, from Halo to Xenosaga, the SIREN series has a back- and side-story that are not apparent just from playing the games. A lot, if not all, of it can be found (in Japanese) in the SIREN MANIACS and SIREN 2 MANIACS books:
Some of the information (still in Japanese) has been posted on the Siren Spoiler Site (already linked in the OP) and, since I don't actually own either of the above books, I'll be posting some information from it. For example, after I went to all the trouble of cracking the "yamibito code" I found there was a key already on this site (although I'm still the first one to translate it completely into English). I assume it came from the MANIACS books, since it includes symbols not actually found in the game.
The official Japanese homepage also has a backstory involving Ichiko, Noriko, et.al. on the Bright Wing and would probably shed some light on what happened. I got it into my head to try and translate it, but then I realized how long it was. It goes on and on an on and it's filled with obscure kanji that I have to constantly look up, so I gave up on that idea. I'm pretty sure that story would be included in the books above anyway.
So anyway, thanks for watching. Be sure to check out the timeline and bonus videos from the bottom of the Index page if you haven't already.