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, then takes him to meet Tiger Tanaka.
At Tanaka's house, the shapely and scantily-dressed Aki unnoticeably swaps with Bond's maseuse 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 Mr. Osato. Leaving after the meeting, he is pursued by gunmen, from whom Aki rescues him again. The gunmen chase Aki's car and she leads them out into the countryside, where a Japanese Secret Service helicopter lifts their 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. He tells her to leave and report back to Tanaka, which she does.
Aki next appears when, after Bond is captured and almost killed by Helga Brandt, she meets with him back at Tanaka's HQ. She and Bond spend the night together, but an assassin stealthily enters where Bond and Aki are sleeping and lowers a thin cord to Bond's mouth, dripping poison down this. At the last moment, Bond turns in his sleep and the poison falls on Aki's lips, killing her. Bond kills the assassin in revenge.
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.