Obtained: During the Chapter 5 Intermission, Maiko will send you a Topic. After you read it, head to Fortuna Office and speak with her.
Maiko wants you to give Nobu some documents at Daiba Studio. Once you accept, you’ll receive an A4 Leather Case. Head towards the map transition to receive an urgent Topic from Kiria. Agree to meet Kiria then travel to Cafe Seiren in Shibuya and speak with her outside to trigger a brief cutscene.
After the cutscene, travel to Daiba Studio to speak with Mr. Horinozawa who is standing in the middle of the room. After the cutscene, you’ll send a Topic to Kiria. To obtain the lens capturing soul, head to the Shibuya 106 Idolasphere. Once inside the Idolasphere, enter the door on the right leading to the Underground Stairs. Head down the passage on the left side of B1F to find the pink mannequin. Enter the sleeve to find yourself on B2F. Follow the path until you reach a T split. Take the path on the right to reach a circular room. The item will be on the ground in this room.
Once you obtain the Illusory Dougen Gem, travel to Bloom Palace and hand it over to Tiki so she can turn it into a lens. Next, travel to Daiba Studio and give the Soulfocus Lens to Mr. Horinozawa who will give you back some documents. Afterwards, head to Fortuna Office and speak with Maiko to trigger a cutscene, completing the side story.