On the next street, Mode Street, you can stop by a little streetfront icecream shop that sells Casteliacones.  These treats cost only 100 Poke each and will restore a pokemon’s status entirely, so make sure you get some when you can- but keep in mind that you can buy only once per day, although you can buy them singly or by the dozen.  The first time you purchase there, a passer-by will immediately stop and wonder about the shop, but nothing seems to actually come of it.

Across the street from the Casteliacone shop is Studio Castelia.  This little art studio has a few paintings and statues, but most importantly a man waits in the topright corner who wants you to show him a pokemon of a particular type.  When you do so, he’ll give you a nice little status-restoring berry in thanks.

After Mode Street is Narrow Street, which is mostly a back alley.  Partway down it behind some dumpsters you’ll encounter a man looking for his glasses- he finds them just as you bump into him, and then tells you that you need more light to see your way and gives you the TM for Flash, a move that mostly proves useless... mostly.

Across from Flash Man (dohohohoho) is Café Sonata, where you’ll get a Moomoo Milk for free on your first visit.  Without Meloetta, there’s nothing else to do here, so head on further into Narrow Street, and you can overhear a really indecipherable conversation between a couple of street toughs.

The last street, then, is ‘The Street With the Pokemon Gym’.  Seriously, that’s as much name as it gets to have.  Leave the Gym alone for now, though, you’ll want to check out the rest of Castelia first.  On the left side of this street is an office building that contains three important places.  The first is its lobby- here lurk a trio of important people: the Massage Lady, the Name Rater, and the Feeling Reader. 

The Massage Lady will give the pokemon of your choice a massage, improving its relationship with you a good bit.  This comes in very handy when you have a pokemon that evolves through its affinity for you.  Since you can use her service every day, you’ll want to make sure you come back to Castelia regularly until all your pokemon that evolve through relationship are done changing shape.

In the middle is the Name Rater, who will rate any nickname you’ve given to your Pokemon as ‘good, but could be better’, and then give you the chance to rename them.  This makes him one of the more-loved NPCs in the game, falling behind only Move Tutors and the Move Deleter.

Last is the Feeling Reader, who stands by the flatscreen television.  He waits for you to do a lot of Feeling Checks with your C-Gear- once you’ve done at least two, he’ll tell you your lucky person for the day out of the people you’ve done Feeling Checks with.

The second floor of the building contains not only a Harlequin, but also the Medal Office.  The lady at the table here will tell you your Medal Collector rank, the hatless man will talk to you about the medals, how they work, and how to do things like set a medal to be ‘shown off’.  The man in the hat just mutters about judging you as a member of the Medal Office staff.

The third floor is Fennel and Amanita’s Lab, where you can go to talk about Game Sync with Fennel.  You can also have a discussion about the Pal Pad and PC Boxes with Amanita.  For the moment this mostly just changes ‘SOMEONE’S PC’ to ‘Amanita’s PC’ in the computer at Pokemon Centers.