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.
Collected all the "Dream Album" files.
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.
Found all hidden items in 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.
Saw three autographs of crazy customers in Somnium.
Day 5: Tuesday - Cleared Mayumi's Somnium.
Had Aiba wear the basket and the pot in Somnium.
Confronted Ota with the evidence with no mistakes.
Day 4: Monday - Cleared #89's Somnium.
Day 6: Wednesday - Cleared Date's Somnium.
Finished Mizuki's investigation.
Almost got cursed by Adorabbit in Somnium.
Cleared the shooting event at the Sejima residence with no misses.
Asked out the receptionist to Atami.
Collected 100 "Appendix" files.
Day 4: Monday - Cleared Ota's Somnium.
Day 3: Sunday - Cleared Iris's Somnium.
Found 6 hidden items in Somnium.
Confronted Iris with the evidence with no mistakes.
Cleared the shooting event at the Kumakura office with no misses.
Enjoyed a fulfilling chat with Kagami.
Saw This Man twice in Somnium.
Finished Iris's investigation.
Day 5: Tuesday - Cleared Iris's Somnium.
Cleared the shooting event at the Warehouse District with no misses.
Day 4: Monday - Cleared Iris's Somnium.
Cleared the shooting event at Golden Yokocho with no misses.
Day 3: Sunday - Cleared So's Somnium.
Confronted So with the evidence with no mistakes.
X-rayed the Mermaid.
Checked absolutely everything in Boss's office.
Day 2: Saturday - Cleared Mizuki's Somnium.
Admired the Sagan's stereo equipment.
Found 1 hidden item in Somnium.
Day 1: Friday - Cleared Date's Somnium.