I feel like iona would be a daughter of the duke who is a high achieving mage and theo would be well off cute/attractive merchant that gains noble status with his achievements.
Iona would be the cold Duchess and Theo would be her orange cat consort hehe
PFFHAHAHAH
Wait why is this so accurate TT
Another could be is Theo the merchant and iona is the mysterious tower lord, trying to start a magic tools business together
I need a reincarnation manhwa w iona as mc and theo as a cold duke of the north