Enishi loves his sister. He is very protective of Tomoe. Even when Tomoe was engaged with Kiyosato, Enishi threw a fit before accepting Kiyosato. At a young age, he already left Edo to search for his sister. Then he met up with the Yaminobu clan who promised him that they will let him and his sister go back to Edo. Not knowing that he was being used, Enishi agreed.
He went to visit his sister who is now living with Kenshin to beg her to come back. Also to tell his sister about the plan to kill Kenshin. When Tomoe refused, Enishi grew even angrier with Kenshin. With that, he stormed out from the house. He thought that everything was Kenshin's fault.
Enishi delivered the letter to Kenshin, about the abduction of Tomoe. He had hoped that Tomoe would go home to Edo with him if he did that. Unfortunately, Enishi ran into the Kekkai forest just in time to see Tomoe killed by Kenshin. Shocked, his hair turned white. Not only Kenshin killed his sister's fiancé and brought her grief, Kenshin also killed her. He vowed to get revenge.
He drifted to China and was adopted by Japanese family who was living in China. He killed his foster family because he couldn't stand their happiness. There, after developing the wushu techniques, and dedicated his life to destroy Kenshin (or rather, Kenshin's happiness). Calls it 'Jinchuu' (revenge). He worked his way up and became some sort like a mafia boss. He was the one who sold the steel ship to Shishio.
When he first met Kenshin, Kenshin was shocked to see him. Enishi asked Kenshin did Kenshin just saw his sister's ghost. He went off and arranged a fight at Kaoru's dojo. He and his henchmen, Gein, Yatsume Mumyoui (who once was in the Yaminobu clan), Inei Banjin, and Otowa attacked the dojo. Kenshin tachi managed to defeat the henchmen. Enishi managed to plant a life like dummy of Kaoru, dead, during the fight to complete his revenge. He kidnapped the real Kaoru and flew off in his hot air balloon. This was to make Kenshin suffer because of the loss of his loved one. It worked… for a while anyway.
When the group found out about the dummy, they rushed off to Enishi's island. Enishi sent another four of his henchmen to defeat them. Kenshin tachi defeated them. It was now Enishi & Kenshin's turn.
They fought. Both are now in serious damage. Enishi, couldn't stand the pain, tore out his ear. He then yelled about how Kenshin had stolen the one thing he wants to protect the most. (Tomoe). Finally, Kenshin sliced Enishi's sword in half. Hei Shin now shot the wounded Kenshin !
Hei Shin aimed his gun towards Kenshin again. But Kaoru jumped in to protect Kenshin. An image of Tomoe protecting Kenshin flashed in Enishi's mind. He punches Hei Shin. Might I add that when Enishi sees Kaoru he is reminded of Tomoe. There was a time when Kaoru was looking at him angrily. The image of Tomoe looking angrily in his mind.
Enishi then was captured by the police. Kaoru handed him Tomoe's diary. I think Enishi then escaped from the police. Enishi now is a wanderer. With Tomoe's diary.