I Am Barberry

I am a barberry tree in the mountains, which has been growing for almost 100 years. Because I am a medicinal tree that has saved many people, the father-in-law of the land promised that I can transform into a human only if I save 100 people and only those who can hear my voice. Waiting and waiting - finally one day I found that person. But he turned out to be a stinky kid who herds sheep. Is this God trying to punish me? Our ridiculous story begins——