Lost Judgment

Observation mode is when you go into first person (click ) and use to focus on objects. It's not obvious what the game counts as a 'target'. But there are plenty of chances to get this throughout the game.

This unlocked for me just after using the Detector (which you get in Chapter 4), so I think 'targets' from this count too.

Here are some that I think definitely do count:

• Chapter 2 (the Sugar Baby) of the Dance Club School Story: Takanashi. She's inside the café
• Chapter 2 (the Turn) of the Casino School Story: find Kohaku in the casino. She's wearing a suit, hat and gloves.
• Side Case #10 (Dueling Dojos), which unlocks during Chapter 3 (Kamurocho). Find Ryan above the door of M Side Café.
• Side Case #8: The Invisible Burglar. Unlock during Chapter 3 through "stalker" keyword (Kamurocho). Go to the south part of Senryo Ave. Find the burglar on the roof.
• During Girls’ Bar school story, the Big Shame Hunter side case you get when you’ve filled Miu’s bar. She was the second bar girl I could talk to. Her bag, and maybe her shoes.