- Estimated achievement difficulty: 2/10
- Offline: 70 
- Approximate amount of time to 1500: 10 hours
- Minimum number of playthroughs needed: 1
- Missable achievements: None
- Does difficulty affect achievements: No
- Unobtainable/glitched achievements: None
- Extra equipment needed: None
Instant Brain is comprised of three games in one. The main game is a standard Japanese adventure game where you make a choice between several options to get to the ultimate ending. It has a twist mixed in, which requires you to take photos and use that photo to prove who the criminal is in each episode. Several times in the game, the game will ask you to point out what’s wrong with this scene in which you need to point out whatever that is. Along with the main game, there are a couple of additional games which is an arcade perfect port of Dodonpachi with Kinect support (don’t worry, you can also play it with the controller if you don’t have a Kinect), and Nin2-Brain, which is same concept as the Nin2-Jump XBLA game but with different puzzle layouts.
Interestingly enough, the game shipped with 1500 gamer score on the disc without any need to download DLCs. The adventure game is 1000, Dodonpachi is 250, and Nin2-Brain is 250.
The notation used in the walkthrough is as follows:
# refers to the choice that you have to make if counted from the top.
Text refers to the actual text of the choice that you have to make.
Make a save in save slot #. (You are to save right before making the choice below this notation)
Load the game from save slot #.
NOTE1: When you are skipping using LT, the game does not stop skipping when you need to take a photograph. You can press LB to open up the back log and go back a few dialogues by selecting the dialogue you want and pressing A. (It may be X. I don’t have the game anymore to double check this.) When it asks if you are sure you want to jump back, select the left option. Make sure to always read ahead in the guide and if there is a photograph section coming up, use A to slowly go through the dialogues or keep tapping LT so that you don’t miss the dialogue.
NOTE2: There are achievements related to the number of pictures you took and number of CG you unlocked. The former is cumulative so if you take 1 picture, restart the game, and take the same picture, it counts as 2, so the achievement may unlock sooner or later than written. (I restarted the game a few times while writing the guide) Same with CG since some photos are included in the CG percentage. If you miss a photo and come back to it after clearing the game once, the percentage will be different and you will get the achievement later than what is written.
The full walkthrough can be found on the forums here: https://www.xboxachievements.com/forum/showthread.php?t=346790
[XBA would like to thank sanger for this roadmap]