The par value of a bond is the amount issuer promises to pay the bond-holder on the maturity date.
The overall return depends on when the bond was bought. The closer to the maturity date, the lower the overall return, or yield-to-maturity (YTM).
If the YTM has been quoted as 9%, it means that the effective yield from today to the maturity date is 9%, according to the current price, and accounting for the 12% coupon, if applicable.
So Devin will earn a return of 9%.