He is smart, wise and is excellent doctor and well skilled hunter since he's hunted all over the world. He really cares about Daisuke always staying close by him, also really cares about his dog John and keeps a close eye on the dogs of Ou. When he thought John went feral he felt responsible as his owner and when he saw that John was no longer here. Hidetoshi felt great remorse over his dog and proud when Andy followed in John's paw prints.
Hidetoshi also felt remorse when he and Daisuke saw a majority of the dogs hurt or killed believing if they came sooner then, Gin and the others wouldn't have gotten hurt. But he makes up for it by helping them now.
Ginga Nagareboshi Gin
He quickly becomes a rival to Takeda Gohei, who always wants to kill Akakabuto. Along with being a hunter Hidetoshi is also a doctor and treats Gohei as he grows ill.
During Gohei's illness Hidetoshi also introduced Daisuke to the hunting bow.
Ginga Densetsu Weed
As years passed, more and more cases of people got killed in the mountains, Hidetoshi got the assignment to kill all the wild dogs of Ōu. He decides to shoot John as he feels responsible as his former owner. It is not until he hears the story of P4 from his former student Daisuke, he finally believes that it is something different and far more deadly than the wild dogs terrorizing Ōu mountains.
Together with Daisuke, he drives to the mountain to find and kill this beast. They find Kaibutsu as Weed and his group is fighting him. As they fall from the cliff, Hidetoshi and Daisuke goes to search for them. They find P4 killed and travel back to Ouu village.
In Hokkaido arc, Hidetoshi and Daisuke hear the news about the stray dogs and pet dogs which went missing from homes and following the puppy Weed. To find out what the dog pack was up to, they follow the pack of dogs to Hokkaido. Upon reaching the destination, they find Weed and the reinforcement pack were in the gorge where there were Ouu soldiers in a bad shape from fighting and imprisonment.
While Weed and his reinforcements went off to find Viktor, Hidetoshi and Daisuke stay behind near the gorge to help the injured dogs (the Ouu Soldiers and some of Viktor's packmates) to recover. Both Hidetoshi and Daisuke also took the severely injured Jaguar, Tābō and Musashi to the vet for treatment.
Hybrid Bear Arc
Daisuke and Hidetoshi drive to Ouu to send Tābō, Musashi and Jaguar back to the wild. Later on towards the end of the story, they drive to Ōu again to visit the dogs - this time they discovered that there were new puppies (Weed's puppies and Jerome's puppies) However, when Hidetoshi saw the German Shepherd puppies (Jerome and Lydia's), he was disappointed that his former pet dog (John) was not around anymore.
Ginga Densetsu Weed Orion
Daisuke and Hidetoshi were visiting the Ōu dogs in the beginning of the story. After they caught some fishes to feed the puppies, Hidetoshi and Daisuke were ready to drive back home when Akame stopped them on the road by barking. This act from Akame saved their lives as there was a minor landslide on the mountain road. The humans returned home safely before another earthquake had occurred.
Soon Hidetoshi adopts a new hunting dog named Andy who happens to be John's nephew, soon he and Daisuke are approached by Rigel and his uncle Kotetsu needing their help. The dogs lead them to the shed where Gin and the others are held.
After they find Masamune's Owner and obtained the key from him to free the other dogs. When the battle with Masamune is over Hidetoshi finds out that Andy has joined the army like John.
Ginga: The Last Wars
Hidetoshi seen for the first time, when he and Daisuke have a helicopter to describe the dogs. They see Ouu army and Hidetoshi ask the pilots to land close. Daisuke seen dead Lydia. Monsoon is hiding in the nearby woods, so they do not see the bears. Daisuke invites Gin, and the dogs running to greet them. Daisuke and Hidetoshi decide to take the wounded Weed and George. Hidetoshi could improve them, and they go out of the helicopter.
Hidetoshi takes care of Weed and George, and later also Gin, who was found wounded from the river.
Whilst caring for the dogs, Jerome is brought in by Daisuke who found the wounded dog outside.
Daisuke tells Gin he has to stay indoors since his eyes are not yet recovered, as he and Hidetoshi are planning to go into the mountains and see what is happening. Hidetoshi grabs his hunting rifle and the two go the mountains. Upon arriving, they see the bears fighting the dogs and stay hidden in the bushes. Monsoon is about to crush Sirius when he hears a gunshot and sees a bear getting shot in the head. The other bears notice the smell of humans and begin to flee, but not before a few more are shot and killed. Monsoon fears for his life and flees into the woods, destroying trees hastily to get away. Hidetoshi and Daisuke begin to check on the dogs.
As they were examining the dogs they discovered the bears the Ohu Army was fighting against were of Akakabuto's bloodline. Seeing the number of dogs that are injured Hidetoshi knows they need help and more people from the village arrive to help and one by one the dogs were taken away for treatment. When Hidetoshi and Daisuke came near Unsai and Akame he sees the white kishu run off with Andy and the others to finish off the bears surprised at their numbers.
Then, he sees Sirius, Zion and Rigel leave after the bears unsure what they are trying to do but Hidetoshi saw that their was some quarrel between the dogs and knew if they don't pull it together they won't win. As they try to treat Unsai the two realized they've ran out of medicine and had to take him back to the vet themselves. Daisuke begins to ask if Unsai will survive and what breed is he; all he could say is he's not sure and that will depend on Unsai's luck and will.
He and Daisuke load Unsai into the van and drive off for the vet. After Unsai is taken to the vet, he tries to get the government officers to work with them. Seeing that they are against Hidetoshi assembles a group of hunters and heads off into the mountains.
After more hunters are guided by the pet dog squad to Hidetoshi, he explains that they are up against Akakabuto's offspring and their leader Monsoon but unlike the dogs they didn't know about Monsoon's great left arm. Prepared for what they were about to face Hidetoshi leaves with the hunters and the dogs finish to off Monsoon for good.
They don't find Monsoon but the rest of his kin and sees that one of them is about to strike Sirius. So he kills three of them and commanded the rest of the hunters and dogs to move in on the bears. To his surprise, he sees that Daisuke has brought a hunting bow and tells hims that they've been outlawed and he'll get arrested if he uses it. Now that he knows the bears can sense danger and seeing that Daisuke is too stubborn to move he and the hunters surround Daisuke to protect him and finish off the bears.
Once the fight is over Hidetoshi counts that a total of 28 of Monsoon's Kin is accounted for, amazed and surprised that so many bears would group together in the same place let alone not try to flee. Hidetoshi started to blame himself that if they had helped sooner, then Gin and the others wouldn't have gotten hurt. But he relishes that he and the hunters were able to help them now but he sees Orion acting funny like the battle isn't over.
He and Daisuke are alerted to the worried barks of the dogs and see Akame unconscious, they find the kishu and revive him, but he is still in a very bad condition and is taken away for treatment. Just before they leave he comments Andy is starting to act like his old dog John.
As time goes on, he and Daisuke leads the villagers in a process of a burial memorial for the Ohu Army's fallen comrades as Orion and the others watch nearby.
He is seen tending to an injured Sasuke and thanks a friend of his for allowing him and Daisuke to use his barn as a temporary vet. Then, he sees Daisuke arrive with Rigel and Orion as the pups see their father again Hidetoshi tells them not to rattle Weed's cage much because he's still recovering.
Returning from the vet Hidetoshi has picked up George and Jerome reuniting them with their friends and checks on Akame.
Then, when checking on Akame he discovers to see that the kishu's eye injury wasn't serious and he fully recovered his sight but Akame had to be treated with eye drops. He told Sasuke to keep his saliva off him and heard someone at the door, for the dogs that survived the fight Hidetoshi called their owners and one by one the pet dogs returned home.
He sees Jerome leaving the barn and Daisuke trying to stop him but he tells him that his injuries aren't serious but he reminds Daisuke that he has to check up on Gin.
See more pictures in Hidetoshi Sekiguchi/Gallery
"The dog is a partner. We are a team, John and I."
- Hidetoshi explains the bond between the dog and the hunter, Ginga Nagareboshi Gin, volume 2
- When Hidetoshi was a teen, many girls had a crush on him, including Daisuke's mother.
- Hidetoshi is a smoker.