The Anime Lad
Prince Oscar bears a curse that threatens his royal lineage, so he climbs a formidable tower to seek the powerful witch Tinasha. She can help investigate. Oscar would also like her to become his wife. Tinasha declines that efficient solution and agrees to spend a year at his castle instead.
Super Eyepatch Fox
Oscar reaches Tinasha's tower seeking a way to break a royal curse. The powerful witch refuses his abrupt marriage proposal but accepts a year-long stay at his castle to research the magic. Their bargain brings court politics and old sorcery into close quarters, with both participants far more capable than ordinary romantic leads.
Gigguku
Oscar walks into a legendary witch's tower and responds to meeting Tinasha by proposing the boldest possible solution to his curse. She has enough power to dismiss him and enough curiosity to investigate. Their one-year arrangement lets magical expertise and stubborn confidence constantly test each other.
Father's Basement
Oscar's opening proposal treats marriage like a convenient answer to a dynastic problem, which Tinasha rightly finds unpersuasive. The better premise is the compromise. She stays at his castle to study the curse, placing an experienced witch beside a prince who cannot simply command her. Their power balance gives the romantic fantasy useful resistance.