On passing the Japanese Language Proficiency Test
Nearly twenty years ago I passed N3, which was not hard after two years of university Japanese; however, the old N3 of four levels is only equivalent to the new N4 of five levels. Hmmm... I have lived abroad most of the time since and studied not at all. I might pass the new N3 only, but I would need to brush up better than my Japanese only good enough for talking with my in-laws and ordering from the menu in izakaya.
Any non-Japanese who gets the N2 is to be respected! Good luck to your friend. Any who get the N1 I am a little suspicious of.* I'd estimate the N2 is equivalent to at least four years of university Japanese language courses.
The essential problem with learning Japanese if you are not Chinese (i.e. read characters already) is that what you cannot read well in Japanese, you cannot read AT ALL: unknown kanji leave one both without pronunciation and meaning, and as Japanese sentences give fewer explicit cues than English (English' mandatory subject, object, person and singular/plural)...
So it comes down to motivation. If one is going to be in Japan for five years or longer, go for N2; if a lifetime, N1. The rest of us are here working in English, whether ESL, international schools or business (or even modelling). I learned a lot of Japanese only when well motivated. Two years in university in anticipation of going to Japan on JET, which I did. The first two of three years in Japan where I had girlfriends (one at a time, usually) who did not speak English. Then I was back 'home' for over a decade. Now I am back, but work and home are in English, and who has the energy to study after dealing with work and a family with two young children. I do finally understand why some immigrants to Canada never properly learn English, or French. On the other hand, if I were in Japan permanently I'd make the effort.
*At least suspicious of the 'Westerners' who do. They often are the type to try to be 'more Japanese than the Japanese' and make themselves, and the rest of us, look very foolish. They have often come to Japan with personal problems. Converts are strange. My father converted between Christian sects and was a fine example.
As many problems as one may have with their birth-culture, whether language, religion, class, etc., it is impossible to avoid or deny. I have many issues with mine by birth: Anglophone, British-Canadian, Catholic, middle-class... However, those things inform who I am, even when I am against them, such as Catholicism: I disagree with the Catholic church's stand on many political, social and sexual issues, but I have a habit of framing my arguments with a Jesuit's logic. The same is true of my best friend, a Reform Jew.
When I see 'Westerners' deal with disagreements with their own culture by suddenly denying their experience and becoming 'Buddhist' or what have you, it is inauthentic. Very much true with 'Japan experts', and Japanese people should be more aware they represent a fairy tale version of Japan that never was to 'the West'. The 'experts' are unaware of their own 'Orientalism'. I have seen the same with Japanese become exaggeratedly 'Christian' (not that a Japanese person cannot be Christian - Endo Shusaku understood Christianity authentically).
We are all damaged people, but it is foolish of those who travel outside of their own culture to think they will not take their damage with them.