The first sunrise refers to the first sunrise of the new year. It is so popular that there are even recommended spots and tours all around Japan to see the first sunrise. The most famous and extremely popular first sunrise would be the goraikou seen on Mt Fuji. Goraikou refers to seeing a sunrise on top of a mountain, especially for sunrises rising above the horizon, and it is an extremely auspicious sign.
There are many people who come from abroad to see Goraikou on Mt Fuji, crowding it to the point that people are unable to climb the mountain.
If you are interested, it’s recommended that you go with a tour.