Well, it depends on which specific comic series you're referring to. In some, they are together, but in others, their relationship might be more complicated.
In this comics series, Edwin and Charles don't end up together. There are various plot developments and character dynamics that prevent their relationship from reaching that point.
A unique plot can make it interesting. For example, if it takes the characters on an adventure outside of the normal Attack on Titan storyline. Maybe they go on a journey to discover a new land or a secret about their past.
One possible aspect of ichika x charles fanfiction could be the exploration of their relationship dynamics. Maybe it focuses on how their personalities complement or clash with each other. For example, if ichika is a very headstrong character and charles is more laid - back, their interactions could lead to interesting storylines.
I'm not sure. But you could look into their business license, brand reputation, and whether they have proper certifications to determine their legitimacy.