First, assume for a moment that nobody really cares whether or not your guests have been to Japan. So what they went overseas for five days. And let us also assume that after your guests return back yonder they show off their pictures to their neighbors, of course the neighbors won’t really care because they can’t really relate to your guest’s experience. They’ll just feign ignorantly on about how wonderful your guest’s pictures are, and how much they envy them.
You get my point?
Nevertheless, one of the best ways to entertain guest in Japan would be to give them a chance to ride on the shinkansen (bullet train), show them Mount Fujii, and if you can, let them take part in a live tea ceremony. Maybe even give them a chance to see Akihabara. Don’t take them to temples unless you have to because you have to assume they know absolutely nothing about Japanese history, and if they did at one point they probably forgot everything. What’s the use of visiting a temple if you know nothing of its history, or could care less for that matter, maybe? Most young Japanese people don’t even care.
If time permits I also recommend taking them to places where they can interact with things, like the Iga Ninja museum where they can take pictures with old ninjas, or even learn how to throw stars called しゅりけん（手裏剣）shurikin. Summer season is usually the best time to for this activity.
You could also give them a chance to dress up like a Maiko or even a Samurai, then take pictures of them and this way they can get a nice laugh when they show their friends at work.
I had a best friend come out here. Nice guy, white guy, New Yoaka, culinary specialist. However, even with all of his gastronomical knowledge he wasn’t able to fully appreciate the Japanese palate.
So here’s the official way I’d entertain guest if I absolutely had to:
1) Food, food, food. Nothing exotic. Start off with recognizable favorites from Japan, like tempura, and yakiniku that way they won’t crave something heavier later on. If their diet changes too soon, coupled with jet lag they’ll enjoy their trip less. Sometimes McDonald’s is okay for lunch.
2) Don’t rely on mass transit to get around Rent a car. Choose easy routes. Just jump on the Kanetsu Expressway and ride it out to Niigata. Show them the backcountry or maybe even Gunma. Get lost a little.
3) Don’t do onsen unless it's mixed bathing. Instead take them to Yunneson in Hakone that way they can spend time walking around in swim suits with you. Remember to try akasuri (あかすり）垢すり, which is called skin peeling in English. Japan will be the cheapest and most accessible place to get it done. Everybody has to try akasuri at least once while they’re here! It’s a must. I get it twice a year.
4) Take them driving driving driving. Sometimes people can soak in a lot more of the surroundings when in a car rather than on foot. Sometimes you do not have to talk the experience away. Let them feel the country for themselves.
5) Shrines are better to visit because they are less crowded. Show them how to wash their hands and teach them a little about the shrines history. Kamakura is the perfect spot for this.
Remember, never forget the wagashi, or Japanese confectionary. It’s a must that they sit down and appreciate some good wagashi. Go to an expensive place, not cheap place.
Lastly, and this is a big one. Remember to take your guest to a real authentic (あかちょうちん 赤提灯 akachochin) or red lantern eatery, which is a place that working-class people can drink inexpensively. The reason being is that they need to experience the real side of everyday working - class Japanese people.