Here is the full list of all 54 Campus Notes - there are forget me not. achievements.
Started the game
Made a friend
Met the three heroines
Met the girl with silver hair
Reunited with the three heroines
Idiopathic Mass Amnesia
Chose to fight IMA
Chose to go home
Chose not to choose
Went after Kaen
Joined Bertha's Knights
Chose to leave the phone
Chose to deliver the phone
Chose to make a phone call
Promised to meet Aika again
Talked with Shion
Talked with Togi
Talked with Kaen
Went to Saiki shrine
Went to Ichinoya Yasaka shrine
Went to Kumano shrine
A feast on Inago and Bee larvae
Chose to believe in a bond
Chose to believe in a curse
Agreed with Kaen
Disagreed with Kaen
Had a date with Shion
Really, it's not a date
Reunited with Shion at the Botanical Garden
Followed Fuma
Talked with Shion and Togi
Walked the Botanical Garden with Shion
Asked to know how Shion feels
Decided not to ask how Shion feels
Talked with Kaen and Shion
Tried eavesdropping Fuma and Shion
Talked with Togi and Kaen
Found out the truth……?
Chose Fuma
Called mom and found out about the time difference
Met Takuma and found out he didn't own a phone
Found out Fuma couldn't get to Akihabara
Spent quality time with Kaen
Spent quality time with Togi
Spent quality time with Shion
Met Niko
Chose to do everything from the start
Reunited with everyone in the real world
Completed Ending: Togi's route
Completed Ending: Kaen's route
Completed Ending: Shion's route
Completed Ending: True route, solved IMA
Saw all event CG's
Unlocked all achievements