The Tenka ("ruler" in Finnish translation) is a mysterious ninja dog who leads a large pack at the tip of Japan.
Legend has it that Tenka's pack comes from a long lineage of ninja dogs that lived near a deadly and volcanic area that is incredibly toxic. It is also said that his ancestors were responsible for the death of thousands of Japanese soldiers who fell victim to the toxic gas.
Tenka has the incredible ability to kill birds with the power of thought, as well as mind control toward other dogs.
Tenka is a very unusual looking dog. He has a slim body, large ears and a long muzzle. He has small eyes with a small bit of black cornea around the iris. He's bicoloured in black and white colour, and has a dark muzzle, light cheeks, chest, legs, belly and tail. He has small spots on his face, and he also has a small moustache or beard-like fur lengthenings on his muzzle. He has two scars on his right side of his face, and longer fur on his lower chest and stomach.
One day, he finds a group of puppies who were put in a bag and were thrown into the ocean by their master. The only surviving puppy was a white dog, to whom Tenka names him Gennai Ogasawara. He then adopts Gennai as his son and Gennai eventually becomes his closest follower.
When he hears from Gennai that the Kurohabaki Clan is in his territory and that the leader, Masamune Kurohabaki, wishs to form an alliance with him, Tenka quickly sees this a threat and refuses Masamune's proposal. Instead, he orders Gennai to set out to assassinate Masamune. However, the first attempt failed after Gennai fought against Kenshin, Masamune's closest follower. Tenka knows that Masamune will try to kill him.
So, Tenka orders Gennai once again to assassinate Masamune a second time. While Gennai is fighting the entire Kurohabaki Clan, Tenka moves his army toward the toxic area and decide to wait for Gennai's return. Gennai and his squad returns from the toxic chasm. Though they failed once again to kill Masamune, they did however lead a portion of the clan into the chasm where they evetually suffacted and died. Tenka is pleased by this and orders Gennai and his squad as scouts to determine the Kurohabaki clan's position.
Gennai returns with four of his five squad members. His squad member, Shiro, stayed behind to further check the clan's position. By nightfall, with Shiro still absent, Gennai and the three of his followers set out to find him. Later, one of Gennai's followers returns to Tenka and pleads him to send reinforcements to aid Gennai's third attempt to assassinate the clan leader.
However, Tenka selfishly sees this as a chance of escaping and orders his pack to move out, saying that Gennai's sacrifice will allow them to escape from the Kurohabaki Clan's grasp. At sunlight, while Tenka's pack heads Eastward to avoid the Kurohabaki clan, they stumbles into Akakamakiri, who was recently banished by his own pack due to his cruel behavior. When Kamakiri's son reacts violantly towards them, Tenka manages to control Akakamakiri's mind, making him bow down as a sign of forgiveness.
Thus, Akakamakiri joins Tenka's pack. Later, Gennai and his battered squad members return to Tenka's pack with Shiro who had lost his ears, eye, tail, and leg. Although Shiro said that he didn't say a word about his pack's location despite the horrible torture that he succumbed to from the clan, the fact that Gennai failed again to kill Masamune was displeasing for Tenka. His final and cruel order was that Gennai and his wounded squad would stay behind and hold off the pursuing Kurohabaki clan as much as possible and to kill Masamune a fourth time.
They then leave the five wounded dogs to the mercy of the clan. They eventually arrive at the secret koga hot springs where Kenshin is resting. One of Tenka's followers quickly notices Kenshin as an enemy, but Kenshin and his followers manage to avoid a fight. Just as they were about to escape, Gennai and his squad arrives. However, when Tenka gives the order to kill them, Gennai, in contrast, lets the clan members go.
Tenka does not understand why his foster son would disobey him and Gennai says that he has decided to desert Tenka's pack. Since Tenka cruely sent Gennai several times into complete danger and even left him and his squad to die like useless dogs, Gennai grew tired of this. Gennai leaves Shiro under Tenka's care and he and the remainder of his squad walk away despite the constant calls of Tenka for them to come back. Later, Tenka and his pack meet up with Sanada Nyūdōunsai and his small pack.
Tenka tries to control Sanada's mind to make him surrender, but this eventually makes Sanada sneeze and he gets over it, proving that Sanada is immune to Tenka's power. However, Sanada kindly bows down to Tenka, saying that they are their "guests". Tenka approves Sanada's kindness and he and his pack rest for a while while Sanada's followers get them food.
Tenka is informed by Unsai about the invasion of Ou by Monsoon and agrees to help out by gathering his army and heading to Ou.
- Tenka is not his name, but a title-name as ruler.