Demonic Spiders: Dragons in particular, especially if there's more than one in the room; they're difficult enough to deal with on their own, but their detailed models and fire attacks are difficult for the console to render, usually causing it to lag enough to make them even tougher to beat. And those fire attacks are probably the strongest attacks leveled against the player thus far.
Game-Favored Gender: Despite being the first Rune Factory game to feature the option to date men, female gamers are quite embittered that their number of choices is far less than the choices for male gamers.
Goddamned Bats: If you've been keeping up with accessory crafting, whatever type of trolls are around can become these. Their attacks may not do much damage, but they usually knock the player back or on the ground; the split seconds of recovery time is just long enough for them to get another punch in. Two of them in a room at the same time can pretty much just do it back and forth, and even if they're only doing Scratch Damage it's a pain to get an attack in edgewise. If you haven't been keeping up with accessory crafting, they can veer straight into Demonic Spider territory.
The Unreveal: Aden and Sonja are still on their home island, but it's 200 years into their future. The dialogue Aden and Odette have in the beginning already makes a heavy implication of this. Specifically, Aden says that Fenith Island is where they come from, but it looks vastly different and Odette admitting that there used to be a lot more dragons flying around, but that they died out over the past few centuries. This Unreveal makes the eventual late-game revelation of Sonja being a descendant of the Wind Dragon Priestess line another unreveal in itself. Once again, the game makes heavy-handed comments about the Wind Dragon Priestess line having 'died out' about 200 years ago.