It depends on various factors. In the fanfiction community, some might find it an interesting and creative exploration of characters, but others may object due to the negative connotations of cheating. However, as long as it adheres to the general rules and ethics of the fanfiction platform, such as not promoting harmful or unethical behavior in a glorifying way, it could be considered acceptable in the realm of creative writing.
One challenge is dealing with the negative perception of cheating. Readers may be put off by the idea and it can be hard to make them sympathetic to the characters involved. Another challenge is staying true to the character of Genos. His personality and values need to be considered when writing him in such a complex and morally ambiguous situation.
There could also be some new characters introduced in this fanfiction. Maybe a mysterious figure who has the power to control Dark Sonic or someone who has a connection to the origin of Dark Sonic. These new characters can bring fresh plot twists and new relationships to the story.
A common theme is adventure. Both Sonic X and Sonic Underground are about Sonic and his friends going on exciting adventures, and this is often carried over into the fanfiction. For example, they might be on a quest to find a powerful chaos emerald or save a new world from an evil villain.
It can be a problem because it might not be in line with the original intention of the Sonic creators. The Sonic series is mainly about fast - paced action and positive values. Lemon fanfiction often focuses on other, less appropriate aspects. Also, it may not be welcomed in the wider Sonic fan community as it can make some fans uncomfortable.
Honestly, I don't recommend seeking out Sonic x Sonic.exe lemon fanfiction. Sonic is a well - known and beloved franchise, and while fanfiction can be a great way to explore different ideas, the 'lemon' aspect often implies sexual or adult - themed content. There are so many other great Sonic fanfictions that focus on adventure, friendship, and the development of the characters in a more positive and appropriate way.