Check in the security room of Evergreen College whether the poster there is not an underflow of the picture of the two girls Michiko and Aoi (timeline 0/real timeline), or what you see there is actually a girl with green hair and a boy with yellow hair (timeline 2).
You can read and download the PDF here, I have summarized a few things I know about all of Crimson Bird games.
The timeline works by changing the temporary fate of the girls helped by Masuo (MC). There are 3 girls whose fates will be saved and changed by Masuo: Junsa, Momoko, and Misa. Currently, you can only travel to timelines 0 (real timeline) and 2. Timelines 1 and 3 have not yet been added.
https://www.mediafire.com/folder/66f5v3rhabzcr/LAGS+Games+Guides+with+Images