Aki played by Akiko Wakabayashi is first seen early in You Only Live Twice. She is first seen when 007 meets her at a sumo wrestling show. Bond knows that she must be his contact to meet Mr Henderson, M's recommended contact in Japan.
Bond looks at Aki and she looks at him, knowing that they have to make contact. 007 makes it clear he is the contact by saying "I love you". Aki drives Bond to meet Mr Henderson. After rescuing Bond from Osato the next morning she takes him to meet Tiger Tanaka.
Aki appears a number of times throughout the next stages of the film accompanied by Tanaka and as an aide to Bond. However before Bond can complete his training as a ninja, Aki is killed. An assassin stealthy enters where Bond and Aki are sleeping where he sends a number of drops of poison down a thin cord. As the poison nears the bottom, Aki turns over leaving the poison meant for Bond entering her lips, killing her.
Aki is a very friendly and happy person who seems to hit it off with Bond near enough as soon as they meet. Aki, as are all of Tiger's men, is a skilled ninja. Bond finds her not only attractive but a useful ally for their missions in and around Tokyo. Aki becomes Bonds lover and he has no questions about marrying her when Tiger says he should take a wife for cover. Tiger doesn't allow this, as it's the job of Kissy Suzuki who takes this role. Aki is unfortunately killed with poison meant for Bond before the wedding can take place.
Akiko Wakabayashi was due to the play the part of Kissy Suzuki but convinced the director that she would be better playing the role of Aki. §