You're not meant to be going through the crack in the wall yet, instead of going there, go up to the north, to the Sector 5 Slums shopping area. This is just after you've come out the church rooftop.
Exerpt
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You'll find yourself in the Sector 5 Slums with a Save Point nearby. Be aware of the random encounters in this area, as there are enemies here called Vice which can steal your equipment. Make sure you kill these thugs as quickly as
possible. The road to Sector 6 (accessed through a hole in the wall on the very left) is blocked for now, so head up to visit the shopping center of the Sector 5 Slums.
The nearby tube contains a sick guy that really 'are sick fo sho', and he's got the number #2 tattood on his arm. It's almost as if someone has been using this guy to experiment on, wouldn't you think?
The big house in the middle houses two shops: The Materia shop is located on the left, but it doesn't sell anything new. The Item shop is on the right, which doesn't sell much worthwhile either. Should you need any Potions, Phoenix Downs, Antidotes or Tents, this is your haven.
Then there's the door on the far right. Enter and head upstairs. Read the flyer on the wall, which is the 'Turtles Paradise Flyer No. 1'. These flyers are part of a sidequest that you can activate much later on in the game. Talk to the
snoring kid and check the locker. Open the hidden drawer, but do NOT take the 5 Gil. If you don't take this now, you'll get a much better reward later.
Lastly, the bus on the upper right part of the screen represents the local weapon store. If you can afford it, buy 3 Titan Bangles and exit the area on the
right.
Check the beautiful garden before entering Aeris' house in order to collect an Ether and the Cover Materia. Feel free to make use of the Save Point as well.
Tip: The Cover Materia will have the equipped character protect other members from physical attacks. It works best to equip the Cover Materia on someone placed in the back row (who takes half the damage of physical attacks). Therefore, long range characters such as Barret are ideally given the Cover Materia since they're usually in the back row.
After meeting Elmyra, head upstairs to rest. Since Sector 6 is such a dangerous area it is probably better to leave Aeris out of your problems and go by yourself, right? When Cloud wakes up, grab the Potion and Phoenix down near the
bed and WALK near the ledge of the stairs to go down. If you only run for an instant, Aeris will discover that you're awake and she won't let you leave. Once downstairs, exit the area and backtrack to the hole in the wall that used to be
blocked....only to meet up with Aeris anyhow.
Make your way through Sector 6 until you reach a playground. Cloud and Aeris spot Tifa on the back of a Chocobo cart and set out to search for her. The cart was headed for Wall Market, so Tifa is likely to be around there .. somewhere.
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Link to the guide this is from.
[Edited by FireflyPoi, 3/8/2011 6:11:40 AM]