[Nagoyankee]

Being a Japanese daddy myself, I can pretty much relate to this father. If he said it, he meant it. He wouldn't have said it in the first place if he couldn't afford it or didn't really mean it literally. I'll be honest. I know you were very much surprised to hear the offer, but it doesn't surprise me at all. I'd probably do the same if I were in his position. Try to think of it as a Japanese style of hospitality.

Now, I understand how you feel about accepting it, but I think you will disappoint this family deeply if you decline quickly. So email again to tell them how you feel honestly and humbly ask if it would be really OK for you to accept the offer. I'm sure he'll reply saying "Don't worry about anything.".