That was my initial reaction too, but the article says "737 with about 100 seats," and the two-class BBJ has only 44 seats, so the indication is that they are thinking of using a regular short-haul 737-700. NRT-RGN is about 2600 nm and a loaded 737-700 has a range of 3400 nm per Wikipedia, so range would not be a problem. Whether customers would accept a "jungle jet" for such a long flight is another issue, of course.