The Investigation Team is a group of students who banded together to solve the mysterious murders of Inaba and explore the TV World.
The Investigation Team is the protagonist team from the Shin Megami Tensei series of games and specifically the Shin Megami Tensei: Persona 4 video game for the Playstation 2. However, in the game the character is unnamed. It's the sixth game of the franchise and was developed as a murder mystery RPG with deep social aspects. It was developed by ATLUS in Japan, directed by Katsuro Hashino, and character design by Shigenori Soejima. It was released in Japan in July 10, 2008, and in the U.S. on December 9, 2008.
The series was later adapted into a manga written and illustrated by Shūji Sogabe, and began serialization in ASCII Media Works' Dengeki Black Maoh magazine on September 19, 2008. The team is first officially formed for manga in Persona 4 Vol. ? Ch. 13 "Kanji Tatsumi Pt. 1"., and the first anime appearance is in Persona 4: The Animation Episode