Aki is first seen when 007 meets her at a sumo wrestling show. Bond is there to meet a contact who will take him to Mr. Henderson, M's recommended contact in Japan. He confirms that Aki is his contact by saying the code words "I love you" to her. Aki takes Bond to meet Henderson in her Toyota 2000GT. After Henderson is killed during their meeting, Bond attacks and kills one of Henderson's killers. Taking the man's place, he is driven to the Osato Chemical Works HQ, where he is discovered by the villains. Aki rescues him, using her skills as a driver, then takes him to meet her boss, Tiger Tanaka. It is after this that a bikini-clad Aki invites Bond to spend the night with her, famously saying "I think I will enjoy very much serving under you", before Bond carries her to bed.
At Tanaka's house, the shapely and scantily-dressed Aki unnoticeably swaps with Bond's masseuse and gives him a kiss. As he carries her away she remarks that nobody will disturb them tonight and that she "will enjoy serving under him".
The next morning, Bond returns to the Osato Chemical Works and meets Blofeld's henchman Mr. Osato. Leaving after the meeting, he is pursued by SPECTRE gunmen, from whom Aki rescues him again. The gunmen chase Aki's car and she leads them out into the countryside, where a SIS helicopter lifts the gunmen's car off the road with a giant magnet and drops it into the sea. She then takes him to a quayside to investigate a ship he suspects is being used by the villains. When investigating the ship Bond and Aki are attacked by SPECTRE henchmen. Bond tells her to leave and report to Tanaka; Aki refuses to leave Bond at first, but eventually complies.
Aki next appears after Bond is captured and almost killed by Helga Brandt, when she meets with him back at Tanaka's headquarters, when Bond is about to go on another mission that she cannot accompany him on. By the time Bond returned to the base in Kyoto, Aki was already fully briefed on the plan to disrupt SPECTRE's plot and she too would be part of Tanaka's ninja force, although (much to her disappointment) she could not play the part of Bond's "wife" in the cover operation, she did however help with Bonds ninja training and in his process of "becoming Japanese".
Shortly after Bond's arrival at the ninja academy, an assassin stealthily enters the bedroom where Bond and Aki are sleeping together and lowers a thin cord to Bond's mouth, intending to poison him. At the last moment, Bond turns in his sleep and Aki moves to his position and the poison falls on her lips which she inadvertently swallows. The poison acts quickly, causing Aki great pain; after a few agonized seconds of gasping for breath, she dies.
Behind the scenes
The original name of the character was Suki. It was changed out of gratitude to actress Akiko Wakabayashi, who had originally been cast as the film's other Bond girl, Kissy Suzuki. It was discovered that Mie Hama, who had originally been cast in the Suki/Aki role spoke poor English and the producers were concerned that she would not be able to cope with the part. They were, however, fearful that if they fired her, she would consider that by being fired she had brought shame on her family, and might commit suicide.
As a result, they built up the role of Suki/Aki, decreased the number of lines Kissy had and asked Wakabayashi if she would agree to switch parts. She agreed, and they renamed the character to thank her. In the finished film, Kissy plays a far smaller part than Aki (and is actually billed after her in the credits), even though she is generally regarded as being the lead Bond girl.
Certainly, Bond builds far more of a relationship with Aki, and may possibly be falling in love with her, as evinced by a scene where Tanaka tells him that when he goes undercover as a Japanese fisherman, the role will require him to have a "wife." Bond immediately looks to Aki, and her pleased reaction clearly shows that the idea appeals to both of them (although Tanaka vetoes it, as the "wife" - Kissy - needs to be an operative who is a native of the region Bond is staking out).
Indeed, Aki is among the more pro-active female characters from the 1960s Bond films, and her character has some similarities to that of Tracy Bond, who Bond would marry for real in the series' next film On Her Majesty's Secret Service. Both are depicted as intelligent women who can take care of themselves, both save Bond from the villains during the course of the story, and both are excellent drivers, taking the wheel during the films' respective main car chases. Bond's reaction to Aki's death is also stronger than similar characters such as Jill Masterson.