Akagi dies at the age of 53, on September 26th, 1999. He figures out he's got Alzheimer's. Akagi hated 'not being himself' because of the disease, and was starting to forget about Mahjong... and his left eye was losing its sight... so before all the big things come he decides to die. Akagi can't bear to be like that.. you'll understand considering his personality and philosophy.
Akagi holds a big funeral prior to his death (he was already very very famous at that point), connects himself to a 'Mercytron' (the kind they use in injection executions), and invites eight of his acquaintances, including Ten, to talk to him right before he dies. Of course they try to talk Akagi out of this, but, as you know, Akagi is firm on his decisions. Books 16-18 (the last books) are all about Akagi and his life-and-death philosophy. 'Life is nothing but a game' and if he couldn't do that, he had no reason to live. As he says: 'I'm stubborn... You can only cure a fool when you kill him'.
Akagi's final thoughts as he dies are 'What's this? Dying is not that scary after all...' He opens his eyes one last time, and then closes them.
After Akagi dies, gamblers secretly take bits of his gravestone for good luck, and so the shape is all ruined. Ten says, "Forgive them, Akagi.. they're doing that because they all like you". Ten and Hiro (another main character) leave the graveyard, and Hiro says that Akagi Shigeru is still in everyone's minds. A cat comes by and sleeps in front of Akagi's now damaged gravestone. The End.