Smiling, the nurse toweled the sweat from his forehead. “You were very fond of Frog, weren’t you, Mr. Katagiri?”
“Locomotive,” Katagiri mumbled. “More than anybody.” Then he closed his eyes and sank into a restful, dreamless sleep.

Murakami ends “Super-Frog Saves Tokyo” on a cryptic note. Just before he dies, Frog says, “The locomotive is coming.” This is a reference to the novel Anna Karenina, by Russian author Leo Tolstoy, in which the title character commits suicide by throwing herself in front of a train. Tolstoy strongly believed in personal integrity and that the meaning of life comes from unselfishly following the path of righteousness. Anna Karenina, however, is selfish, fixated on the opinions of society. Unable to be true to herself, she sees no way out besides death. When Frog alludes to the locomotive in the final seconds of his life, he signals his own awareness of his imminent death.

Frog references Anna Karenina earlier in the story as well, when he says that if Katagiri abandoned him on the battlefield, he would go on fighting alone, even though he’d have about as much chance of defeating Worm that way as Anna Karenina had of defeating the oncoming train. This first reference to Tolstoy’s novel is not arbitrary. Frog staunchly believes that his mission is a righteous one. He warns Katagiri that the two of them may die underground and that even if they are successful, they will never be recognized for their sacrifice. Katagiri seems to accept this at the end of the story when he falls into a “restful, dreamless sleep.” He realizes that society doesn’t need to know about the sacrifices he’s made—either in the battle with Worm or in his previous life—because he made them to satisfy his own internal sense of virtue. Katagiri comes to accept Tolstoy’s philosophy, as Frog has before him, that self-gratification doesn’t lead to happiness. One finds harmony by following the dictates of one’s inner integrity.