There are four interesting things I would like to point out in this short video from a par 5 hole on a golf course in Central Japan. Three of these things, all potential mysteries on their own, I explain here, but for the fourth I asked for your assistance in solving the mystery.

1. The cart has no driver. This is a remote-controlled five-passenger cart, commonly found on golf courses in Japan and Korea. The cart takes the clubs around, allowing golfers to walk as much as they want to. I've always been concerned, being involved with course maintenance, about these quiet carts that can sneak up on you. One must be careful of what I have termed "ghost carts!" Note the concrete rails upon which the cart drives. This eliminates traffic damage from wear or compaction that would occur if the cart drove onto the turf.
2. The grass on the fairways is manilagrass (Zoysia matrella). The grass in the rough is japanese lawngrass (Zoysia japonica). At this course, as is common in Japan, there is no irrigation system in the fairway or the rough. Both species of zoysiagrass survive in this climate without supplemental irrigation. In this type of climate, without irrigation (or with judicious application of water), zoysia can provide a firm, bouncy playing surface with plenty of roll.
3. There are two greens on this hole! This course uses the two green system. Most courses with the two green system have the main green as creeping bentgrass with the subgreen being used less often. The subgreen is usually still creeping bentgrass but sometimes will be Z. matrella or bermudagrass. It is interesting at this course that the main green is Z. matrella and the subgreen is creeping bentgrass.
4. And now for the mystery. Why are there tee markers in the fairway? We can see that the golfers are not using them. Do you know what the markers are for?

Answer: These tees are called "playing 4 markers" or tokusetsu tees. Why "playing 4"? Because the purpose of those tees, commonly found on mountainous courses or on courses where the carts travel in a fixed (and pretty much unidirectional) route, is for one to hit from after a ball has been discovered to have gone out of bounds, or has been lost. Thus, when one hits from that point, one is "playing 4" or hitting one's fourth shot on the hole. 

Thanks to everyone who sent their answers to this mystery. I didn't realize it would be such a difficult one to guess. I, unfortunately, am too familiar with "playing 4" markers, having made use of them many times after errant drives. In addition to "playing 4" markers, some courses also place a flag or wind sock as an aiming point in the fairway.