Sesshomaru, the "human," slaughtered them all with a single stroke of his arm. He then turned his attention to Naraku, who was trapped inside his body after being defeated by Sesshomaru. Using his blood, Sesshomaru created a seal that would imprison Naraku forever.
After this, Sesshomaru went on a journey throughout Japan, freeing those who had been cursed with immortality. At the end of his journey, he came across a village where a young girl named Nagi was about to be married off to an old man. He stopped the wedding and asked the villagers what kind of god they were worshipping. When no one answered, he decided to take care of the problem himself. So, he started killing everyone except for Nagi because she seemed like the only person who didn't worship him.
Years later, when Nagi became a priest, she remembered what happened and used her skills to track down Sesshomaru. She found him living in a cave near their village and confronted him about what he did. Sesshomaru told her it wasn't his fault and that he did what he did because nobody else would.
Although Sesshomaru had no regard for humans or inferior youkai, he had often demonstrated that he was a noble creature by saving Inuyasha's life when he was hurt or went insane. Rin showed kindness and cared for Sesshomaru after he was hurt and weak after battling Inuyasha, a human he had always viewed of as weak and despicable. When she needed help the most, it was Sesshomaru who saved her. This proves that even though he lived in fear of being killed by Inuyasha, he still had feelings for Rin that went beyond hatred.
When Sesshomaru first met Inuyasha, he attacked him immediately because he wanted to kill him for dishonoring his family name. However, when Rin came into their lives and started caring for Inuyasha, he began to see him differently and stopped trying to murder him every time they met. He also helped nurse Inuyasha back to health after he was injured in the battle with Shikon no Tama.
Finally, when the two were about to fight to the death, Sesshomaru used his powers to turn himself into a seal and protect Rin while she was inside the house. This shows that even though he hated humans, he would do anything to protect those he loved.
That is why his father gave him this sword; he knew how Sesshoumaru first treated humans and less strong demons without mercy. It was around this time when Sesshomaru was harmed by Inuyasha's wind scar. His injuries were severe, and he spent the time he needed to heal in the woods. When he returned home, his father had already started training him so that one day he could be a ruler like them.
During his training, Sesshoumaru met many strong warriors who wanted to be his friend. One day he went to visit them all at their homes because there was to be a battle between the best fighters in our world. He wanted to choose his friends so that they would be there to support him during the fight.
Sesshoumaru was about to make his choice when he saw Inuyasha being beaten up by his brother Kikunojin. The sight of this innocent little fox getting hurt made Sessthoniruhoko (his favorite weapon) weep blood. With tears in his eyes, Sesshoumaru raised his sword high into the air and shouted "Kikunojin no Jutsu!" (A technique from Kikunojin). With a flash of light, both Sesshoumaru and his sword disappeared!
Inuyasha didn't know what happened to him until he found Sesshoumaru's son Shion walking in the forest.
Inuyasha began to hit Sesshomaru, but the illusion vanished, implying that everything was all in Inuyasha's brain to begin with. Following Mukotsu's death, Naraku directed the surviving Shichinintai to assassinate Sesshomaru as well. When they failed to do so, he commanded them to continue hitting him until he died.
After being saved by Inuyasha, Sesshomaru told him about his father's murder at the hands of Naraku. This prompted Inuyasha to seek out Naraku to avenge his friend's death. However, when they reached the palace, they found it empty except for Naraku, who was using Sesshomaru's body as a host. Inuyasha tried to attack Naraku, but was defeated easily. Before leaving, Inuyasha promised to return one day and kill Naraku once and for all.
Two years later, Inuyasha returned to the palace looking for more clues about Naraku's whereabouts. He discovered that someone had been living there recently, so he waited outside while some servants went inside. To his surprise, it was Naraku who came out looking for him! Overwhelmed, Inuyasha begged for mercy, which Naraku granted. They then talked about what had happened two years ago before Naraku left to search for more hosts.