Now the Pokemon Go: Shiny Pikachu and Raichu Present in Japan
There is no announcement made by the Niantic about the addition of the rare form of Pikachu and which comes in a dark yellow shade and had a shiny animation but those people who visit the Pikachu outbreak event which was held Japanpan are able to hold them.
Now, as we talk about the shiny Pokemon:
The shiny Pokemon will be now available, but it is not yet been conformed that the new shinies are available outside of the Japanese events or not. There are 2 Pokemon which were available in the shiny form i.e, Magikarp and Gyarados.