Below is a walkthrough for the Make Some Medicine task in Rune Factory 5.
Client: Yuki
Objective: Craft some medicine using the Chemistry Set
Reward(s): Toyherb x1
This task will show up on the Task Board after completing the Buy a Chemistry Set task. Accept it and Yuki will ask you to mix some medicine. The easiest recipe to make is the Recovery Potion which requires a Green Grass and Medicinal Herb. Both of these items can be found growing near your farm in town. After mixing the medicine, return to the Task Board to complete the task.