[Editor’s note: The content of this post has been deleted for the following reason: That is a terrible idea, and you clearly need adult supervision. Again. An edited version of this post is below.]
It’s difficult to handle a pokémon that displays oddly romantic feelings towards their trainers for two reasons. First, letting down humans is difficult enough, and we actually speak the same language and, by and large, can empathize with one another. Second, unlike humans, pokémon wield power over the elements, so angering or upsetting one is a risk.
That having been said, though, as with letting a human down, a trainer must exercise tact and clarity when communicating with an overly affectionate pokémon. Establish boundaries and be sure to tell your pokémon firmly when they’ve crossed them. Unlike humans, pokémon communicate in a very simple manner, so when you tell them no, they usually will take your no at face value, rather than cobble together an interpretation based on your body language.
However, like humans, pokémon may get upset or confused by the existence of this no, so it’s important to establish an amicable but clear relationship thereafter. If your pokémon reacts poorly, calm them with treats, training, or forms of affection that cannot be interpreted as consent. (Petting, for example.) When dealing with more human-like pokémon, be sure to keep a physical amount of distance and follow up your no with activities that clearly establish the master-pet dynamic, such as training.
In short, tell your pokémon very clearly that you don’t wish to have that sort of relationship with them and that it’s uncomfortable for you but be sure to establish what your relationship is shortly afterwards with entirely platonic activities.
Good luck, anonymous!
The Pokédex According to Bill 