Iji 1.7 - Official game guide|
Introduction - Sector 1 - Sector 2 - Sector 3 - Sector 4 - Sector 5 - Sector 6
Sector 7 - Sector 8 - Sector 9 - Sector X - Sector Y - Sector Z - Misc secrets
Unlockables - Weapons - Items - Enemies - Bosses - Trivia - Text dump
The first Sector is pretty easy and straightforward, and most of the secrets rely on increasing your Strength stat.
Located in the top-right part of the large room in the middle of the Sector, you can easily reach it from either side of the room it's in. Like the rest of the ribbons, if you don't pick this up, Iji will forget about Mia and not see any further ribbons for the rest of the game. Ribbons won't appear on Single Sector Play or Sudden Death Sector.
Each sector has a poster. To find this one, increase your Strength to 2, and kick down the door to the left of the starting point. There are some informative logbooks from the scientist team here as well.
These pickups give you a permanent extra Point, which you can spend on upgrades. Nothing special happens when you find them all, and they're not required for anything. To find this one, increase your Strength to at least 4, and go to the top floor (A). Kick the nearby Tasen Soldier down to the left of her platform, and lure her to the left. She'll fire a rocket and destroy the wall next to the lift, allowing you to pass through to the secret room (B).
Secrets + notable modifiers
Sector Z entrance
To the left of the Supercharge (B), there is a teleporter that requires unlocking all ten posters to enter, leading to Sector Z. Logbooks in Sectors 3 and 9 normally reveal where this entrance is located. Note that you can enter a Sector, find its poster and immediately exit to the Main menu, and it will still count as having found the poster.
Hardcore hair accessories
Hitting your head on 12 or more ceiling lamps produces a hidden chat at the end of the Sector, with a unique portrait for Iji. This was added after nearly all of the betatesters did this.
Dan thinks outside the box
Playing on Ultimortal or Sudden Death Sector changes some chats which would otherwise describe impossible tasks, like obtaining the Machinegun, and reminds you of the special rules for those game modes.
In the background to the left of the ribbon room, there is a small jar with a Reaver from my game Hero on top of a crate (C).