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.
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.
Collected all the "Dream Album" files.
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 Iris's investigation.
Day 5: Tuesday - Cleared Iris's Somnium.
Saw This Man twice in 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.
Collected 100 "Appendix" files.
Day 3: Sunday - Cleared So's Somnium.
Confronted So with the evidence with no mistakes.
X-rayed the Mermaid.
Finished Ota's investigation.
Day 5: Tuesday - Cleared Mayumi's Somnium.
Had Aiba wear the basket and the pot in Somnium.
Saw three autographs of crazy customers in Somnium.
Confronted Ota with the evidence with no mistakes.
Finished Mizuki's investigation.
Day 6: Wednesday - Cleared Date's Somnium.
Found 6 hidden items in Somnium.
Almost got cursed by Adorabbit in Somnium.
Cleared the shooting event at the Sejima residence with no misses.
Asked out the receptionist to Atami.
Day 4: Monday - Cleared Ota's Somnium.
Day 4: Monday - Cleared #89's Somnium.
Day 3: Sunday - Cleared Iris's Somnium.
Cleared the shooting event at the Kumakura office with no misses.
Confronted Iris with the evidence with no mistakes.
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.