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
This Sector is entered by landing the final blow on General Tor in Sector X with the Null driver (acquired in Sector Z). It's basically Sector 1, but almost completely empty. Since there's no way out you need to press Escape and choose to go back to the main menu.
Secrets + notable modifiers
Also at (A) is a logbook that tells you to enter HORSEGUN on the main menu. This lets you play Missile Pony X starring Horsegun Punchesbullets. Make sure to check out the information in the Pause menu by pressing Escape. While Yukabacera's highscore (actually mine) is listed there, beating it doesn't reward you with anything. See "Ultimate secrets" under Misc secrets for more information.
Betatesting quotes logbook
The logbooks in sector Y are empty, except for the one at (B). It has quotes from the betatesting and voice recording sessions for the game.
Clown mode logbook
At the end of the Sector (C) is another logbook with text in it, telling you how to toggle clown mode by holding down and Enter for ten seconds. This can be done at any time without having read this logbook. In Iji 1.5 you had to read this logbook thrice to see the message.
Star Fox / Starwing
Sector Y was based on Out of this dimension, a bizarre secret level in Star Fox that could not be completed.