Teddie serves as the guide for the Investigation Team in the Midnight Channel. At first, he acts as support for battles, but after the party completes the Marukyu Striptease dungeon, he joins in combat, while Rise Kujikawa takes over the support role. Whenever a new team member joins, Teddie is inexplicably able to create glasses so that they can see through the fog in the Midnight Channel.

Teddie was first seen in the Midnight Channel at the time when the protagonist, Yosuke Hanamura and Chie Satonaka search for an exit, after leaving the Ominous Bedroom. Teddie, confused and irritated by their presence, asks them to leave because it's dangerous there and shows them the exit. After Saki Konishi's death, the protagonist and Yosuke enter the TV again in order to investigate. There, they meet Teddie once again, but he gets suspicious and thinks that they are the ones who've been throwing people in. After they try to prove their innocence, Teddie asks them to find the real culprit and makes them promise to do so in order to let them out. When the protagonist first awakens to his Persona, amazed by his power, Teddie immediately calls him "Sensei." He assumes the support role for the team until Rise Kujikawa joins the party.