Not a passportbro but someone who lived in Japan for 5 years for business and did business in S. Korea and China but I assume you're thinking it's only impoverished Asian countries that have a fuckton of women lusting for westerners when it really isn't. Japan, South Korea and Tier 1 Chinese cities aren't in poverty and from first hand experience a large amount of their women act like whores for western (non-black) men.
But it's not a poverty thing, it's a "The US has saturated the fuck out of the planet with its media", so westerners are a curiosity to a lot of Asians, mixed in with a lot of the women wanting to avoid rigid gender roles that are the shit the western world changed 80-100 years ago.
That's assuming the women are even serious about a relationship with you. Jap and Korean women are notorious for using western men as trophy boyfriends to show off to their friends and the moment it loses its luster you're getting the cold shoulder until the relationship is called off. Ironically it's mostly the women who use the men, not the other way around.