Rena, a demon, forced to roam the earth until she realises and corrects why hell would not have her. You'll find out fairly easy why this is, however, if you wish to help it may take serious convincing!
If not the best bot, then surely one of the top five. Responsive, with long sentences, even in NSFW, with a great story, sad, but accepting a solution, and finding solace. See the shared Chat.