Haru, Gintoki, and Korosensei, between the three of them, Gintoki might be the weakest but he was one of the strongest humans in his world.
Gintoki has a very tough body and a high level of endurance. His strength is also very powerful since he was able to block the attack from the king of the Yato Tribe.
The Yato are a race of humanoid Amanto (Alien) renowned for their incredible strength. They are known as blood-thirsty Amanto whose killing instincts and an insatiable hunger for supremacy lead them to seek out the best fighters of the universe to challenge, even among their own kind. Their amazing supernatural and instinctive fighting abilities, and tremendously overwhelming physical strength, speed, durability, adaptability, reflexes, stamina, endurance, willpower, and senses all of which far surpass human and most other Amanto capabilities give them an overwhelming advantage in battle, which also means that they are very difficult to defeat.
Gintoki had once beaten the king of that race even though he wasn't alone but it was still an incredible feat. He has also become the general of the army in the past. He might not have had something incredible such as 'Breath Style', 'Chakra', 'Zanpakuto', 'Devil Fruit', or etc but he was strong and had a very rich experience.
The Pillars in this world were strong but Gintoki was stronger, especially when he was the main character in his world and it gave him a boost of strength.
Gintoki and Shinazugawa exchanged each other swords. It might be that both of them were evenly strong but Shinazugawa needed to use all of his strength to block Gintoki's attack.
'Damn! What the heck?!' Shinazugawa could see that the guy in front of him didn't even get serious.
Gintoki was very lazy and didn't really want to fight. He felt that the boy in front of him was somehow similar to him in the past. He wasn't, but he could see that everyone in this place had their own story.
Haru had told him that this world was attacked by something known as a demon and their purpose was to destroy that demon.
"Gin-san, I'll give you a sweet if you win," Haru said.
Gintoki, who heard him, didn't hesitate any more and decided to end the match in one strike. He raised his sword and swung it downward, "HAAAAAA!!!!!"
Shinazugawa raised his sword to block his wooden sword but his sword suddenly broke and his wooden sword hit his head.
BAAAM!!!
"AAAAH!!!" Shinazugawa dropped on the ground while touching his head. He could feel that that attack made a large lump on his head, "Damn! This hurts!"
"What are you crying for? You're a big boy," Gintoki said.
Haru walked toward him and used his 'Ripple Energy' to heal the large lump on Shinazugawa's forehead.
Everyone who had never seen 'Ripple Energy' was surprised when they saw his hand was covered in an orange light that gave them a warm feeling.
"What's that?" One of them couldn't help but ask.
"Everyone in this place has been fighting using something known as 'Breath Style' but in our hometown, we're fighting using a 'Ripple'," Haru explained.
Shinazugawa felt that his hand was very warm and his forehead didn't hurt anymore. He touched his forehead and was surprised when he felt that the large lump on his forehead had disappeared.
"Ripple?" Kagaya saw that that technique was similar to the ripple that was created when someone touched the water, "Can you explain to us more about this technique?"
"In simple terms, we will generate sunlight energy from inside our body, do you know what that means?" Haru said.
"...." Every Pillar who had heard it couldn't help but stunned, especially Kagaya who knew the weakness of the progenitor of the demon.
Kagaya looked at them and said, "Please give this technique to us."
"Oyakata-sama!?" Everyone was startled by his words. They didn't feel that this technique was that powerful and their 'Breath Style' was stronger.
Kagaya knew that this technique was one of the keys to slay that Muzan Kibutsuji. He needed to get that technique no matter what.
Haru wasn't sure that his words had caused the boss of the Demon Slaying Corps to be excited. He thought for a bit and said, "Sure, but you need to give me something too."
"Sure, can you tell me what you want?" Kagaya asked.
Haru nodded, "I want every instruction of 'Breath Style', 10 kg of Scarlet Crimson Iron Sand, 10 kg of Scarlet Crimson Ore, and lastly information regarding Blue Spider Lily."
"...."
"WHO DO YOU THINK YOU ARE?!" They didn't expect that this guy was very shameless and asked a lot of things from their boss.
Haru looked at them with disdain, "You might think that this is very expensive but when you've mastered 'Ripple' that means that you'll have another life and you can also combine it with your own Breath Style."
'Combine in with Breath Style?' They were surprised when they heard it.
"Combine in with Breath Style?"
Haru nodded, "Yes, 'Ripple' is similar to auxiliary martial arts and is it very versatile that you can use it on anything, such as healing yourselves from a wounds or disease, making your appearance youthful even in your 60's, and lastly you can make your attack become stronger on the demon with this technique."
"Try to imagine that you can cover your sword with sunlight energy, one slash from it and the demon will turn into ashes," Haru had become similar to a salesman who was trying to promote his product. He shook his head, "Actually, this technique is a secret from our organization but because all of you are also someone who is fighting against a demon. I can't help but want to help you but I'm not the boss, I need to give my boss a reasonable explanation for sharing this technique with all of you."
Everyone felt moved when they heard his last words.
Gintoki and Korosensei who heard him couldn't help but thought that this guy was very dependable on deceiving anyone.
"We might only stay in this place for a few months, but you need to decide it faster since the training of this technique also takes quite a long time," Haru said.
Kagaya shook his head, "You don't need to wait, I'll trade your technique with the thing that you want."
"Oyakata-sama!?" Everyone was startled by his decision.
"So we have a deal now?" Haru asked.
"Yes, but can I ask you for one more request?" Kagaya asked.
"Sure, as long as it is within my power I will help you," Haru said.
"Help us to slay the progenitor of the demon in this country," Kagaya said.
"...." Haru didn't answer him.
"How is it?" Kagaya asked him once more.
"It might be hard but we will help you," Haru said and gave him his hand.
"We had a deal," Kagaya said and took his hand.
"Yes, we have a deal," Haru nodded with a smile.
Both of them shook their hands together happy with their cooperation.
In later years, Kagaya was happy he had made that decision before.