i smell 20 years old situatioship type deal between them they are definitely in love but they never dated nor even kiss or anything, it's purely yearning on both side, they want each other badly but never crossed the line. because the duke is dead-ass he doesn't even hide it but Mahen always dismiss it as an annoying jock. And the duke think that he will never reach Mahen heart so he stick to flirting without ever taking it further. which reinforce to Mahen the idea that he's simply joking. 