The third band member approaches you, but doesn’t talk to you on her own- this gives you a chance to shuffle your team and apply items if you like.  You can trigger your battle with the leader of this little group by talking to her.

Battle: Guitarist Tina (1056 Poke)
Opponent: Krokorok Lv 33, Liepard Lv 33

These three are fairly tough, but nothing you shouldn’t be capable of handling by now.  Keep an eye on the Scraggy, as it uses Chip Away to bypass resistances.

With all three members of the group defeated, the guitarist declares you the Boss of the area, also claiming you deserve a medal.

With the band beat, check to the left and you’ll find Blackglasses lying around.  This handy item boosts the power of Dark moves when a pokemon holds it, adding a nice solid 25% to their attack strength.  With the raw utility of Dark attacks (resisted only by Steel, Dark, and Fighting) and the variety of pokemon that can learn them, this is a very useful hold item.

Return to the sewers from here and head East a touch to encounter another janitor looking for a fight.

Battle: Janitor Brady (1240 Poke)
Opponent: Marill Lv 31, Cinccino Lv 31

Beware of Cinccino’s Cute Charm- this one is female, unlike its trainer, which is a bit unusual.  Infatuated pokemon don’t do well in combat.

Return West and South to the water, heading South again.  Follow the route to the East back onto land, then cross the wood bridge going South.  Immediately turn and head East across the wood bridge there, then North across two more bridges.  Talk to the Doctor there if your pokemon need a healing, and use the door near him to check with the female scientist for another healing item.