For Clorica you have to trigger two events first: "Get it Together" first, and then "An Ephemeral Wish" (this latter one being the marriage event itself, and it being unique in that you are prompted to give her the Engagement Ring in the event itself rather than after it). Before doing these 2 events you cannot marry Clorica.
As for Leon Karnak... I'm sorry, I can't remember any specifics, but if you teleport to the Obsidian Mansion and just go straight left, you should get to it, I don't remember being blocked by anything. --- 3DS: 3239-2567-4999 PSN: NatatBW XBL: Natatdood Mains: BBCP: Bang - P4A: Liz - AE: Cammy/Ibuki - 3s: Makoto - MBAACC: H-VSion/C-Ryougi - GGXXAC+R: May