Soon after the Chapter 2 case, you'll receive another Holo Clip by moving out onto North or South Boulevards: Looker has another case for ya. He's concerned about Emma: ever since we decided to house her here, she's been appearing stressed out. Soon thereafter, a woman speaking Japanese (whoa!) enters the bureau.
Obviously, our in-game selves cannot understand it, and you probably don't either. (It turns out it's basically just what you're told moments later - it's comprehensible, just not really special.) After Looker clearly misunderstands the woman, Emma arrives, seemingly able to speak both Japanese and English.
Apparently, Mimi is able to provide a sort of telepathic translation. Afterwards, we find out the real reason the woman came: to find out who stole her Pokémon. Emma posits that the thief was part of the Lumiose Gang; Looker goes off to Lumiose Station to find them, without a Pokémon to help. rolls eyes
Well, go off and help him - within the station, go to the east end of the southern platform. Hurry up and defeat those punks before their poor grammar gives us a brain hemorrhage. Should your Pokemon take a battering, speak to Looker to heal your Pokemon free of charge.
Trainer Battle: Lumiose Gang Member Sedna
Trainer Battle: Lumiose Gang Member Eris
Trainer Battle: Lumiose Gang Member Nix
After defeating the punks, the chapter will wrap itself up and all your troubles will be over. For the time being anyway.