[tyranuus]

Aye, they could do a sequel, they left it open enough for one, but unlike a lot of series, with the final scene between Mina and Akira, it doesn't necessarily need one.

I think whether it gets another series will depend on the cashflow from this one; if its popular, they've left it open enough they can return to the property and continue where they left off, with more of Akira/Mina as a developing couple and a new plot arc and antagonists, or if they don't get a chance to produce another series, the series has an adequate sense of closure.
Even if they didn't answer everything, there is still closure on the main focus of the series which was Akira/Mina's relationship, in the sense they are obviously now together at the end of the series, and that last scene could virtually be taken as a marriage proposal in it's own right. (After all, with her winning the gambit on the Duke's 'game' she won the right to be with whomever she wanted and break free of the marriage agreement)