The Hayashi-nettai Mountains are a chain of steep, jagged mountains in the east of Tatsu. The mountains block most of the breeze coming off the sea leaving the area very warm and humid. Because of this the mountain range is home to many forms of exotic plants and Pokemon normally only found in warmer climates. Also found within the mountainous area is the resort city of Kuroi as well as the Black Forest, famous for its many superstitions and urban legends surrounding it.
Because the range is so warm and humid do to the lack of a breeze off the ocean to move the air around the Hayashi-nettai Mountians have become home to a wide variety of exotic flora and fauna. Pokemon trainers brave the ragged drops in search of creatures that prefer warmer climates such as Chatot, Tangela, a variety of bug Pokemon, and Vileplume to list a few.
In its early history these mountains were home to the ancient villages of Aoki, Jakk, and Secorro the descendants of which would eventually build the modern day city of Kuroi. In its bloody past all three villages would collide for years before attacks from the Black Leaf Resistance would prompt the construction of New Aoki over the site of the village of Secorro. New Aoki would expand in several phases until it filled the valley formed by the mountains and was renamed Kuroi.
Over the tops of the trees in the low areas of the mountain range it is possible to see the massive towers and many coloured lights of Kuroi. Despite its violent past Kuroi has evolved into a resort city where vacationers can go for all forms of entertainment, shopping, and fine dining. most recently Kuroi is home to the Fairy type Pokemon gym led by Pixie Fay. Here trainers wanting to obtain the Legend Badge can challenge the gym leader to an official league match.
There are rumours that at the base of the mountains there are cave systems which if followed will lead you in to the Kuroi Valley. It is said the valley floor is devoid of plant life and is extremely cold due to the city overhead.
The Black Forest is a wide forest stretching several miles between the route connecting Shiidara City and Gaston Town and the foot of the Hayashi-nettai mountains. This area is famous for its urban legends, hauntings, and superstitions. Reports of paranormal activity are common in this area which causes problems for people wishing to get into Kuroi city on foot as you must pass through this forest to reach it from the mainland. Tourists wishing avoid the forest must make motorized travel accommodations in one of the surrounding towns to be driven into the city or can take a ferry from Centria to the Southern Pier in the outskirts of Kuroi.
Theories about the reasons for the activity are numerous, none however have been adequately researched to confirm or deny any. Popular theories include ghosts from the regions violent past being trapped in the mountain range; the mountain range's geological location provides it with a strong field of paranormal energy which opens spaces to other dimensions; as well as ghost type Pokemon who have taken up residence in the forest chasing out intruders.