The idea of Eren Yeager in a harem scenario is interesting because it takes a character from a serious and often dark story and puts him in a more light - hearted, relationship - focused situation. It allows for different character interactions that we don't see in the original work.
The key to doing a man bun comic is having a clear idea. Maybe it's a day in the life of someone with a man bun or a humorous adventure. Draw the characters proportionately and use colors or shading to make it stand out. Don't forget to proofread for any mistakes.
Such a description might be used to make the character stand out in a fanfiction. He could be a unique character in a fantasy - based fanfic too. For example, he could be a wizard who has adapted to some modern - day human habits like wearing a hair tie on his wrist. His bun could be a way to keep his long hair out of his face while he's performing magic.