Enter Beetle Forest for the first time. Koris will be there waiting to train you. Talk to him, then go to attacking and defending. He will give you a free Mugwort to start with. Then, disobey his commands while in training. He will make you start over, but you will still have the Mugwort. Repeat this process to get free Mugworts.
Jade Cocoon: Story Of The Tamamayu