Jade Tower Pearl is one of six mystic art upgrade materials, there are two ways to get Jade Tower Pearl.
The first way is to gather Jade Tower Peoney for a chance of getting Jade Tower Pearl. Here are Jade Tower Peony exact location on the map:

Jade Tower Peony spawn scattered inside Kaifeng City as well as the northeast outside Kaifeng city as well.

Note: It’s not guaranteed to get Jade Tower Pearl all the time but we can increase the chance of getting it by:
Eat Golden Jade Soup from Fuling Shop:

When eating this food, you’ll gain 20 minutes of higher chance of gathering Jade Tower Pearl, so always eat this food first before you start gathering.

The second way is to buy Mystic Skills Breakthrough support box from from Season Shop and Battle Pass Shop:

You can buy 10 Mystic Skills BreakBreakthrough Support boxes per week from Season Shop. Costing you 5000 Jade Fish.
You can buy 3 Mystic Skills Breakthrough Support boxes per week from Battle Pass Shop. Costing you 15 Battle pass tokens.
You can get a total of 39 Jade Tower Pearl from this method, but we don’t recommend getting all Jade Tower Pearl as you will need other material for other mystic art as well.
In conclusion, To get Jade Tower Pearl, you need to eat Golden Jade Soup from Fling shop, start gathering Jade Tower Peony, if you’re lucky you might get Jade Tower Pearl, or you can just buy it all from both Season shop and Battle pass shop.
Other Mystic Art Upgrade materials:
Beauty's Plume | Vicious Fruit |
Buddha's Tear Root | Jade Tower Pearl |
Jasmine Stamen | Frost Mushroom Mycelium |
End.

Beauty's Plume
Vicious Fruit
Buddha's Tear Root
Jade Tower Pearl
Jasmine Stamen
Frost Mushroom Mycelium