Before returning to Brainheart, Kai went to another shop to get some ingredients for his new potions. The Royal Potions didn't sell ingredients, so there was no reason to ask for it there.
In fact, Kai had something else in mind. He wanted to get some seeds and plant his own ingredients. With the magical soil in Brainheart, it wouldn't take long for the herbs to grow. It was way faster there.
Also, it would be cheaper, and Kai would get an infinite supply of herbs. He was a beginner at making potions, so he knew he would use a lot of resources to produce the novice potions.
There weren't that many shops selling ingredients. They often used the ingredients to make their own potions, so they saw no reason to sell them.
'Maybe I can learn where to get the ingredients myself? That would make everything way easier.' Thought Kai.