I’m going to step in and throw you an idea that’s not quite answering the question:
I suggest that, if your brother-in-law is in Japan, he seek out one of the many good private schools for English. There’s a whole industry built up for the purpose and, when they’re not teaching High School students in the mid-afternoon, they take in a steady clientele of Salary-Men in the evenings (and housewives in the early afternoon).
For the beginning students (it sounds like he will probably start as a beginner, even though he probably had English classes in grades 6-12 already) the school at which I taught would start by ‘teaching’ people Japanese folk tales in English. The point was to start from a base that was familiar to them and add a layer of foreign language. I happened to be familiar with the material because I grew up (in the States) on a compendium in English called The Dancing Kettle (and other Japanese Folk tales). I see that it was a 1949 publication and Amazon shows it’s apparently super expensive. On the other hand, Amazon shows A Treasury of Japanese Folk Tales: Bilingual English and Japanese Edition by Yuri Yasuda, Yoshinobu Sakakura, Yumi Matsunari and Yumi Yamaguchi which might be quite convenient for your engineer friend.
For a more grown-up approach, you might see if he is familiar with any Japanese ghost stories and provide a collection of them in English as translated by Lafcadio Hearn. You can even find transcriptions of Hearn’s two volumes as free books for the Kindle; search by author name. Also free for the Kindle is another Hearn collection called Kwaidan: Stories and Studies of Strange Things. Be forewarned, though: I would estimate that Hearn’s collections are above beginner-level English. Your brother-in-law might be more familiar with the name Kaidan or HyakuMonogatari Kaidankai.
[For that matter, the Tale of Genji has been translated to English and it’s also free for the Kindle, but I didn’t find the content very interesting so I wouldn’t recommend it as a comparison piece for learning English.]
He might also visit KinoKuniYa or a local bookstore and find art books in both English and Japanese – often published by universities and art museums and republished with translations for foreign markets. Often they will have captions in both English and the target market’s language. The main text will generally be in the target market language (though sometimes they’ll have facing pages in original vs target language, which is great for comparisons.
Folk tales are not just stories for children.
They are vehicles to convey the culture and values of a society to each generation
even before they are able to understand the underlying lessons.