Thanks man. Collecting two stones in the hidden doors does the trick.
Also, I read in the old post, to activate Loki event, I have to go to B04 area. What do you mean by B04/B03 area?
Loki's route:
1. Do her quest and get the scene with the insignia on the wall.
2. Find the special coffin lid in the lab. Trigger the event with Lilica at the house.
3. Sleep until Micri leaves employment.
4. Sleep one more day. Talk to the receptionist. Unlock new external dungeon.
5. Complete the external dungeon. Get Micri's first scene.
6. In chapter 5, defeat any enemy in the region close to the pink pillar. There'll be a scene with Micri asking if player is prepared to enter the new dungeon. Choose yes.
7. Beat the dungeon boss to get Micri's final scene and remove her insomnia debuff.