"Devil Survivor 2 Record Breaker is an enhanced port of Devil Survivor 2 made exclusively for the Nintendo 3DS. The port features voice acting for most if not all dialogue, a casual mode, a new female character, and a new scenario that takes place after the battle with the Septentriones that can be accessed from the start of the game." -Megami Tensei Wiki
Izaya appears in the second half of the collab event requesting a knife of this world as well as a snack with personality. Upon being given these things, he provides players with the Shady Informant's knife.
Upon completing various quests for Shizuo, players can receive Ikebukuro's Strongest Man Sign, which is a melee weapon shaped like an uprooted street sign. Shizuo's outfit also grants a unique skill and can be acquired by the player.
Celty is one of the first characters to appear during the collaboration. After players bring her various fairy demons, they can receive the Headless Rider's PDA COMP. Her outfit could also be acquired with the helmet unequipped. Female players wearing the outfit would appear headless.
Visit Megami Tensei's Wiki for more information.