The Ending Seems Clear to Me
Yet another explaination? Yes.
Are Ichi and Kakihara the same people? No.
Anyhow, there seems to be a lot of debate about the ending and it all seemed pretty clear to me so here goes...
Since Ichi couldn't kill Kakihara, (Ichi was too busy crying about killing Kaneko who he thought was his brother), Kakihara says out loud that there was nobody left to kill him.
Kakihara couldn't stand the fact that Ichi wasn't going to kill him. Since Kakihara hadn't been that scared or excited in years he was hoping that Ichi would give him a glorious gruesome death. Kakihara said that every time over the years that he would get so excited and scared about someone, it always resulted in a let down. He stated that he worried that Ichi would be a let down and hoped he wouldn't be.
Upon seeing Ichi crying in a pool of snot and crying uncontrollably whilst the young Takeshi kicked the tar out of him...Kakihara was CRUSHED as this was the biggest let down in the history of all letdowns that not even could have forseen.
To drown out Ichi's crying, Kakihara pokes out his own eardrums and fantasizes that Ichi beheads the boy, Takeshi, and then comes to finish off Kakihara, slicing his forehead open and causing him to fall. Kakihara is imagining all of this and is actually jumping to his death pretending to have a glorious ending.
Jijii seems happy that Kakihara is dead because he can now collect the rest of his money that Suzuki promised him, but realizes that Ichi is useless to him and must be left behind. He's not saddened by it, but he is a bit sombered by it and he drops the bag holding Ichi's belongings and leaves them behind before walking off.
Jijii knew that Ichi's mental state had been worsening and that he had been getting harder to control. By telling Ichi that Kaneko was his brother Jijii knew that Kaneko would have to kill Ichi, or Ichi would have to kill Kaneko. Either way Jijii knew that Ichi wouldn't return because if Ichi believed that he killed his brother, his mental state would make him useless for further jobs.
Later we see Jijii hanging from a tree, who is killed several years later by Kaneko's son Takeshi. We know this is Takeshi because he is wearing the same outfit as he did on the rooftop and the bird flew by him as he turned around which reflected the earlier scene where he fed the bird by hand.
Basically it explained what happened to pretty much everyone in the end, except Ichi who was left on the rooftop crying and being kicked by Takeshi.
Overall I thought it was a really good movie. The CGI was a bit hokey in spots, but the acting, story and originality really won me over.