man used for free rides; designated driver (slang)
Dated slang from the bubble era; refers to a man who is kept around mainly to drive a woman around for free. Often used in the context of dating or social circles where the man's car is the main attraction.
See also: 足 (あし)
She apparently keeps several guys around just for free rides.
The term アッシー君 was popular during the bubble era.
From 足 (あし, 'legs' or 'transportation') and 君 (くん, familiar suffix for males). The term plays on the idea of a man whose main function is to provide transportation.