I would not assume that I think. The better universities vis a vis Japan are certainly overseas, but there are many Japanese parents, (some schools are nearly 70-80% so, that send their kids to Jr. HS and Sr. HS to learn English and then re-enter the Japanese system to be fully qualified Japanese grads with rocking English skills. The kids often end up doing all the regular int’l school work plus a healthy dose of Juku on the side. Nightmare-ish, but it gives them an edge entering he job market locally. There are likely very few Japanese parents who would consider the US schools a better choice as undergrads but would very much consider them for a year abroad or a Master’s degree. So much of a person’s marketability here is tied to the name of the institution they attend as an undergrad. Fp0r that alone I thin k it is a career killer for Japanese students whose parents hope they live in Japan to send them overseas as undergrads.
Not to say she is wrong, but in 27 years I have only missed some specific people, pizza, Mexican food and good barbecue. Besides that Japan is an awesome place to live.
Am holding the printout I got from the Nenkinjimusho that shows how much I will be due when I retire and it is triple what you state. I think this is due to the fact my form requires us to pay into a higher level insurance plan, but still as it is an option for all, and a requirement in my industry, 180-200K is much more realistic if you want it to be.
My contributions are a lot more than £120 a month too though.

Oh I don't dispute that people who have Kosei Nenkin and/or their own private plans will get more in payouts.
What I am comparing like for like is the absolutely bog standard basic pension with no sprinkles on top.
The point I was trying to make is that the UK basic state pension is a much better deal than the Japanese one.
Because I work remotely for a UK company I am Category 1 (as though I was self employed here in Japan) so I have to sign up to the Basic State Pension - I don't make contributions through Kosei Nenkin.
(Note I do have a private pension plan as well but just wanted to highlight the differences between the UK and Japan basic state pension)