Here is the full list of all 45 AI: The Somnium Files achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Obtained all other trophies.
Found all hidden items in Somnium.
Collected all the "Dream Album" files.
Saw This Man twice in Somnium.
Almost got cursed by Adorabbit in Somnium.
Had Aiba wear the basket and the pot in Somnium.
Saw three autographs of crazy customers in Somnium.
Found 6 hidden items in Somnium.
Confronted Ota with the evidence with no mistakes.
Confronted Iris with the evidence with no mistakes.
Confronted So with the evidence with no mistakes.
Finished the final investigation.
Discovered the marriage of the yakuza and the nurse.
Kept your cool and did not shoot Saito.
Collected all the "Persons" files.
Day 6: Wednesday - Cleared Saito's Somnium.
Finished Annihilation Route investigation.
Day 5: Tuesday - Cleared Boss's Somnium.
Cleared the shooting event at the Sagan residence with no misses.
Day 5: Tuesday - Cleared Hitomi's Somnium.
Confronted Hitomi with the evidence with no mistakes.
Finished Ota's investigation.
Day 5: Tuesday - Cleared Mayumi's Somnium.
Day 4: Monday - Cleared #89's Somnium.
Finished Iris's investigation.
Day 5: Tuesday - Cleared Iris's Somnium.
Cleared the shooting event at the Warehouse District with no misses.
Collected 100 "Appendix" files.
Day 4: Monday - Cleared Iris's Somnium.
Cleared the shooting event at Golden Yokocho with no misses.
Day 3: Sunday - Cleared So's Somnium.
X-rayed the Mermaid.
Finished Mizuki's investigation.
Day 6: Wednesday - Cleared Date's Somnium.
Cleared the shooting event at the Sejima residence with no misses.
Day 4: Monday - Cleared Ota's Somnium.
Asked out the receptionist to Atami.
Day 3: Sunday - Cleared Iris's Somnium.
Cleared the shooting event at the Kumakura office with no misses.
Enjoyed a fulfilling chat with Kagami.
Day 2: Saturday - Cleared Mizuki's Somnium.
Admired the Sagan's stereo equipment.
Checked absolutely everything in Boss's office.
Day 1: Friday - Cleared Date's Somnium.
Found 1 hidden item in Somnium.