"basics" of korean and japanese will get you no where.
I dont see why you want to do your speciality training in japan if you're 1) not fluent, 2) not a national.
Being a doctor/surgeon is a very serious career that requires excellent communication. how can you expect anyone to hire you when you aren't fluent in the language? patients need to be comfortable with their physicians and a physician that requires a translator or doesn't understand rural speak will be seen as incompetent.
plus being a doctor in a foreign country requires much more than just understanding the language, as a doctor you'll be expected to learn immense medical vocabulary. all the antomy and medical terms you've learnt in english will become irrelevant, you will have to relearn everything in japanese or korean by yourself, no one will have time to translate for you.
this is not to mention the competition you will have from actual japanese citizens for the same post.
japan is notorious for its tight immigration controls, its very difficult for an IMG to get a job there.
I dont know much for korea.
the culture and way of life is very different in both countries. i cant speak much for korea, i am japanese myself (half, my father is japanese and mum is from canada) people work very hard, most doctors hardly get to spend time with their families and there are incredibly high expectations of doctors. if anything goes wrong profound public apologies must be made and these fields are always competitive.
Not to mention the simple fact that a foreigner simply will never be regarded with the same respect and competence as a japanese doctor in japan. its sad but its discrimination that still exists in japanese culture. even hafu japanese people like me struggle to be accepted as regular japanese people, though things are changing. as a doctor patients will always trust a japanese doctor more than a foreigner, especially if you're not a native speaker.
Plus its going to be a long road to even get a license to practice there as a foreigner.
sorry to burst the bubble.
As for cost - living in tokyo is more expensive than living in london + much smaller accomodation. flats are tiny in comparison to uk. its difficult finding accomodation.
the best route for a non-japanese hoping to train in japan was to have gone to a japanese medical school, build your reputation this way/make connections and learn all the basics of medicine in japane, medical terms in japanese and the culture of how medicine is practice in japan.
as an IMG (international medical graduate) you will struggle to be considered and you will find yourself feeling very unhappy and lonely if you cannot speak nihongo, you wont fit in with the culture and people.
Dont delude yourself into thinking you can get by with 'basics' of a language. its fine if you want to go to japan to teach english or open a resturant. but to go into a serious profession like medicine, you need to 100% fluent. this is a field that requires very high levels of trust and communication and someone who cant be bothered to become fluent will not be taken seriously.
Plus a patient will think something like "why should i go to a foreigner who speaks japanese okay when i can be treated by a japanese doctor?"
unless you truly intend to practice in these countries, then doing speciality training there is pointless and waste of time.
most people do their speciality training in the country they intend to practice in/become full time doctors or surgeons in. for example i'm originally from canada and though i'll be getting my medical degree in the UK i intend to complete my speciality training in canada because thats where i want to live/practice for the rest of my career.
the process of getting a license to practice medicine in japan as a foreigner will be VERY difficult for you.
if you were planning to move there for a simple job where you didnt mind people treating you like a clueless foreigner and not trusting you then thats fine, but for a profession like a doctor/surgeon which requires so much trust, communication and most of all RESPECT, you will struggle and end up very depressed there.