Put it at the exact beat where Shinji finally turns toward the camera, then follow it with Anime Ahh for an over-the-top reaction, or use Awkward Moment afterwards when nobody else reacts to the thing he just noticed.
About this sound
This is a short, roughly two-second voice clip of someone shouting 'Did you see that, Shinji?' with urgent, excited energy, as if demanding that Shinji look at something right now. It feels playful and teasing rather than angry, turning a simple call for attention into a joke aimed at anyone called Shinji. The direct name makes it instantly personal and easy to aim at a friend.