Akihito is the current Emperor of Japan. In real life, he acceded to the throne in 1989, upon the death of his father, Emperor Hirohito.
In "Whale Whores", he reacted badly to Stan Marsh's leadership of the Whale Wars crew. He explained to them that the atomic bombings of Hiroshima and Nagasaki where allegedly caused by whales and dolphins, but grew even more angry when Stan "revealed" that the chickens and cows did it and had "framed" the whales and dolphins.
He appears as a faithful recreation of the real-life Akihito.