I like how they actually explained why Liona has 4 ears. So it isn't standard with all kemonomimi type animal girls, but it's because she's half-human. I guess the human body is a target of convergent evolution with features that have dominant genes in their world based on how "Purebloods" could produce Type I offspring.
Railguns require obscene amounts of electricity, which is a a major issue why these weapons haven't yet gone past experimental stages into mass production in the real world. I guess power isn't a problem over there, their hurdle is in manufacturing and materials science?
If the physics and chemistry in their world is very similar to his, judging by how electromagnetic waves work the same way... they could probably invent nuclear weapons too, provided as a high schooler from Japan he has at least some idea about the principles of atoms and nuclear chain reactions. But he was kind of a delinquent back then. Maybe they won't go that far.