It's a new thing that appears on the Niconico maps. They are on the 3rd tab missions and cost only 10 stam for... just nothing. It give you less than 100 gold (with the boost) ans 2x25 gold from first 3 medals it. There is 3 stages. The first one is really easy. The 2nd and 3rd need 640k Total Power. And I guess it give nothing more.
And it seems to be limited missions.