As of the latest chapters I've read, Megumi is still alive in the manga. Usually, such major character deaths are significant plot points and would be well-publicized if they occurred.
Maki in fanfiction usually has a fierce loyalty to her friends, especially Yuta. She is the type to fight for what she believes in. Yuta is sometimes portrayed as being a bit naive in the ways of the world outside his own small circle, but his pure heart makes him endearing. In many stories, their different personalities create an interesting dynamic, like in a story where Maki's boldness gets them into a risky situation and Yuta's calm thinking gets them out.
Typically, megumi fanfic often focuses on his personality traits. His stoicism and determination are often highlighted. For example, in many fanfics, his unwavering resolve in the face of danger is a central theme.