In this fic, both George and Izzie died in 5x24. I don't own Grey's, unfortunately.
Mark Sloan slowly walked up the stairs to Meredith Grey's attic. He had a vague idea of what he wanted to say to Lexie, but he wasn't sure how it would pan it. And being nervous wasn't something that Mark Sloan was entirely comfortable with.
He found her sitting in the corner of the room, clutching onto a pillow for dear life. She looked so small and wounded, and all he wanted to do in that instant was take her pain away. But he wasn't sure how to, or even if it was possible to, so he was glad when she spoke first.
"I'm not part of the group. Meredith and Cristina and Alex all have each other, but I'm not in that group. George and Izzie were my friends, but I wasn't one of 'Bailey's Five,' so it's like I don't get to grieve. You know, George was the first person to be nice to me at Seattle Grace. Yeah, we'd drifted apart after he became a resident and we took out Sadie's appendix, but he was still the first. So that's special. And Izzie took an interest in teaching me. Well, and the other interns. She made us feel like we mattered in the hospital, even though we're the bottom of the Surgical Food Chain. But I guess Izzie thought that even the bottom has a purpose. But, now, they're gone. And I'm back to having no one. Because I was stupid and said things that cost me you. So I have no one."
Mark sat down next to Lexie and took her hand in his, knowing that this was his moment to tell her his feelings.
"You are not alone, Lexie. I'm here. You haven't lost me. I love you too much to let you go. So I'm here. You can cry and grieve, and I can be a punching bag if you want me to be. I'm staying. Because you're my everything. And on a day like today, you need to know that you're my everything."
And with that, Lexie knew that everything would turn out okay eventually. Because she, Alexandra Caroline Grey, was Mark Sloan's everything.
"Did you say it?'I love you. I don't ever want to live without you. You changed my life.' Did you say it? Make a plan. Set a goal. Work toward it, but every now and then, look around; Drink it in 'cause this is it. It might all be gone tomorrow."