The real answer is of course "it's complicated", but i'll take a shot:
Since the 80s, Japan has been seen as very 'futuristic' in the west. Some combo of extreme density and a high percent of the economy being manufacturing makes people more comfortable with technology, and that's reflected in their pop art and music, on top of the normal exoticism of a non-western language and culture.
Aside from this, their (extra future-y) nerd culture is more accessible to westerners through manga, anime, and video games than countries like China or India.
They also have fewer taboos about mixing sex and digital entertainment, so things like dating sims and porn games probably draw a segment of the particularly digitally comfortable into Japanese culture.
Since i visited Japan (and some other asian countries) i will try to explain my own fascination of the coutry: It's the fascinating mix of high-tech and tradition.
Japan is very high tech, but remained relatively closed to other countries for a long time. They have their own religion (Shinto). Their own alphabet. Compared to other asian countries (like indonesia) people have a different mindset.
All in all, it fits the right amount of familiar-but-different for me. For comparison: Singapore is just familiar-with-an-asian-touch to a westerner.
I'll add to this. Every place has its ups and downs, and the cultural distance allows Westerners to completely miss the negatives. Normally this is canceled out because the majority of nonwestern nations are visibly poor.
That means it can just seem incredibly cool and fun, while it's actually a relatively boring country in the scheme of things
Since the 80s, Japan has been seen as very 'futuristic' in the west. Some combo of extreme density and a high percent of the economy being manufacturing makes people more comfortable with technology, and that's reflected in their pop art and music, on top of the normal exoticism of a non-western language and culture.
Aside from this, their (extra future-y) nerd culture is more accessible to westerners through manga, anime, and video games than countries like China or India.
They also have fewer taboos about mixing sex and digital entertainment, so things like dating sims and porn games probably draw a segment of the particularly digitally comfortable into Japanese culture.