Agreed that the job would look very good on resume, plus just simply knowing JP practice, some Japanese, etc.
What happens after the 2 years are over?
The back and forth will be hard though, but if it isn't forever (ie the rest of your career), then it is worth considering.
My husband spent one month periods back and forth for a year followed by 6 months apart, and it was hard. Not only when he was gone, but even when he was back. Re-adjusting to life together, knowing that in just a few weeks he would be gone again, I spent the first two weeks re-adjusting to living together, and the last two weeks mentally preparing for him to leave again, then the entire month he was gone waiting for him to come back, repeat.