I have such a weakness for like. mundane au petribell where Simon is either divorced or a widower and is just wallowing in his own depression and self-hatred and Fionna is an also-depressed neurodivergent 30 year old who takes an interest in his cool antique and art collection and eventually becomes friends with him and they fall in love and/or have sex and Simon can’t get out of his own head about how he’s a creepy old predator taking advantage of a young woman and grooming her, when essentially Fionna is the one who willfully inserted herself into his life and took an active role in progressing their relationship to a sexual level. and while in real life this would be a very nuanced situation, in the context of the fanfic it’s very clear that the social power dynamic is in Fionna’s favor, which isn’t to say she did something unethical because Simon was obviously consenting, but more like, it’s not a big deal dude, you’re torturing yourself over nothing.