The train is going to a world where every single human being is male. Although it’s not as popular as the female world one, the male world train still gets many passengers. Maybe there are a handful of slow nights where the train doesn't take anyone, but that's not enough to shut it down.
There’s still gender expression, with more feminine men mostly doing chores in their houses, but fundamentally, zero women exist in this world. A hundred percent of the human population has XY chromosomes, with a penis, scrotum, and everything that comes with those. Most of history still happened, but the only difference is that all women were men instead.
When it comes to sexuality, all men are homosexual, although masculine/feminine relationships are the most normalized. Men can get pregnant if their dominant partner ejaculates semen in their anus, but anatomical structures are mostly similar to our world’s men.
It’s a pretty exciting train to get in. For some people, it means reaching a better world, while for others, it’s just a way to experience something new.