My biggest fear possibly sounds ridiculous (especially for author with 150 subs ), but...
What if someday I'll become famous, and some comics/manga/anime company will convince me to sell them rights for using my characters and setting, and... and...
...they will take a SOUL and INDIVIDUALITY away from them?!
Like... they will turn my MC into stereotypical "cool guy" and "computer genius". He will slap her ass, call her "baby", tell Cool Jokes in the middle of the battle. She will perform absurd "genius" hacking, typing at keyboard at the speed of light and saying nonsense with randomly mixed IT words. And then, instead of the normal plot, they will go into standard pop-style adventures, at the end of which they will fight GREATER EVIL and save the world!!! (of course, in the final battle boi will fight evil boi, hacker girl will fight evil hacker girl, and cat will fight evil cat) But the most horrible it will be, if they will win that final fight... OMG... BY THE POWER OF THEIR LOVE?!!
NOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!
You probably laughed, but one night I've accidentally imagined it, and couldn't sleep...