In Chapter 6 of Lost Judgment, examine the bulletin board in Yagami Detective Agency to obtain The Saga Continues Ryan’s Rival Appears! job request. Make your way to M Side Cafe on the corner of Theater Ave. and Taihei Blvd. Once you enter M Side Cafe, you’ll be tasked with finding Ryan. Press R3 then examine him clinging to the wall above the stairs. After the cutscene with Ryan, you’ll receive the Ninja Outfit! Follow the objective to the far southeastern corner of the map to find a ninja standing guard. Speak with him then equip the Ninja Outfit disguise. Speak with the ninja again to gain entry.
A chase will be your first trial. Catch Kalashnikov. For your second trial, you’ll need to play a game of darts. The last task will consist of a ninja fight. Defeat all the ninjas to reveal the true reason everyone wants to join Kalashnikov’s school. After a long cutscene, the case will close and you’ll receive the Training Band.