Need to come up with a suitable antagonist or problem. Maybe a perverted magical artifact, a rival trying to sabotage, or a curse from a previous witch. The story needs to resolve with Jessica's growth.
Also, the Crest Witch title might tie into a specific magical ability, like her crest allows certain spells but she's not using it properly. The Crest could be a family inheritance or a mark.
I should create some conflict. Maybe the school is hosting an event, and Jessica's antics get out of hand. Perhaps she's trying to prove herself, but her lewd behavior is problematic. Maybe there's a lesson in responsibility, or maybe a humorous resolution where her lewdness is actually the key to solving the problem.