You can get the Seal Case from a woman in a house on the eastern outskirts of Solaceon Town. You don’t need to do anything special to get the Seal Case—just speak with her and she’ll give you one for free.
The earliest point that you can obtain the Seal Case is just after defeating Leader Fantina at the Hearthome City Gym.
Where To Find the Seal Case Woman
After winning the Relic Badge from Leader Fantina, the next leg of your journey takes you through Solaceon Town.
On the eastern side of town is a heavily-wooded area. There are a couple of houses hidden in the forest here, and it’s in one of these homes that you’ll find the woman who provides the Seal Case.
To reach the Seal Woman’s home, start by heading north from Solaceon Town’s Pokémon Center.
Just before you reach Solaceon Town’s northern entrance, turn right to enter the gap in the woods.
Go past the first ledge and instead drop down the next ledge after it.
After dropping down a second ledge, enter the front door of the house right next to you.
You will find the Seal Woman standing to the left of the table inside.
Speak to her and she will hand you the Seal Case at no cost.
She will also give you an assortment of five randomly-chosen Seals.
Note that you can also speak with her son on the opposite side of the table to earn more Seals. You’ll do that showing him various forms of Unown caught from the Solaceon Ruins.
Seal Case Details and Uses
The Seal Case is used to store Seals, which are special stickers that create visual effects in battle when affixed to a Pokémon’s Poké Ball using a Ball Capsule.
While the Seal Case isn’t a necessary item, you won’t be able to collect any Seals if you don’t have one.
The Seal Case can store 99 copies of each of the game’s 77 total Seals. You can check how many total Seals you have by opening the Seal Case from your Bag’s Key Items pocket and selecting Use.
How To Apply Seals to a Poké Ball
You will need to use a PC to actually affix the Seals to Ball Capsules. Any Pokémon Center PC will do.
First, boot up the computer and select your trainer PC.
Then, select Ball Capsules from the next menu.
You will be presented with a list of Ball Capsules to decorate. To start customizing one, choose any empty Ball Capsule and select Edit.
The touch screen will display a list of all the Seals in your case on the left side of the screen, which you can then drag and place on the Ball Capsule on the right side.
You can see a preview of the effects the Seals will create by tapping on the Ball Capsule icon in the bottom-left corner of the touch screen.
This will play the Pokémon’s “entering battle” animation as it will be seen by other players.
You can save a maximum of twelve Ball Capsule configurations—basically two full Pokémon teams’ worth.