I feel like doing a startup in Japan is not yet cool, from a general society perspective.

I think that almost every one of these new founders are having regular arguments with their parents, who would be trying to convince the founders to get a "real" job at a "safe" company.

Having said all that, I agree that inexperienced people often give up at the first speed bump. As Steve Jobs said:

“The problem with the Internet startup craze isn’t that too many people are starting companies; it’s that too many people aren’t sticking with it.”

That's a good point about the older generation. I have a few friends who feuded with their parents when they quit a very very good engineering job at a big company to do their own thing instead.

That being said I do think that doing a startup is perceived as being cool by their peers. I've met at least a handful of people who I'd cautiously call "fangirls".

(Perhaps an overflow from their perceived coolness of working in SV/SF -- which honestly doesn't make much sense to me since their motivations to cross the pond is often profoundly lacking in substance)

Working in SV/SF and doing own startup is surely sounds different things to me, as an Japanese grad student

Sorry, to clarify: many young people seem to see the whole SV/SF thing to be cool and seem to almost idolize the prospect of working in the promised land. By association startups as a whole (regardless of location) are cool to them. As a result startup founders in Japan get additional social support from their peers for their endeavors (which as you know is a huge psychological benefit in Japanese society).

Almost doesn't matter. If any significant number survive to reach success then it'll change everything, eventually. It's very difficult to argue against success, e.g. millions in the bank accounts and products that people are talking about. And once people see their friends and former coworkers succeed they start to get the idea they can do the same.