Black egg look a bit like this. The website said that it's available for 500yen at the Owakudani egg steaming hut. Alternative is I got it at the Souvenir shop at the opposite of Hakone Yumoto station, level 2, in the cold section for a little over 200yen and it's cool and refreshing to eat (I like).!
Every day, 25,000 tons of hot spring water gushes forth from the 17 hot spring sources of Hakone, making the area fifth nationwide in terms of spring water volume.In addition, there are approximately 20 different types of hot spring in Hakone including simple alkaline springs, common salt springs (containing sodium chloride), gypsum springs (containing calcium sulfate), and others. It is possible to compare this hot spring resort area to a five-story department store (B1F–4F): acidic sulfate springs at the highest elevations are on the 4th floor, while bicarbonate sulfate springs are on the 3rd floor, chloride springs are on the 2nd floor, and mixed-type chloride bicarbonate sulfate springs are on the 1st floor and basement level. Today, hot spring water is extracted from even deeper portions in the volcanic crater's outer rim.
Since ancient times, Japanese hot spring areas have been developed as tourist destinations. Hakone, which is filled with many tourist attractions, has taken up a lead position among such destinations—this can be seen clearly in the fact that Hakone is top in Japan in terms of number of lodging facilities, visitor capacity and number of lodging facility guests.
Source: Hakone-machi
