Throughout his run the Shining Knight never had a steady romantic interest. In Adventure 155 (Aug 50) Sir Justin meets Mary Mason, and in chivalrous fashion approaches her father for permission to date her.
It turns out Mr. Mason is very into Arthurian lore as well, and wants Sir Justin to prove himself worthy of his daughter. He sends him into a swamp to fight “dragons” (lizards), but Sir Justin stumbles across some escaped prisoners.
He gets into his Shining Knight gear and defeats the felons, saving Mary in the process, and while the father is suitably impressed, Mary is not. She credits the Shining Knight with her rescue, and believes Sir Justin did nothing to help her.
And so ends Sir Justin’s big romance.