'baki oc fanfiction' basically is fan - created stories centered around original characters in the Baki world. Some might be action - packed, with the OC showing off their fighting skills against Baki's foes. Others could be more about the emotional side, like the OC forming a deep friendship or a romantic relationship with a character from the original Baki story.
Well, you could try looking on specialized Indian streaming services that often have a wide range of foreign dramas dubbed in Hindi. Sometimes, local TV channels also air such shows.