Kobayakawa Ami is Takara's childhood friend. She got hit by a car because she pushed Takara out of the way when he was bending over to pick up a ring that he had gotten for Hikaru.

Spoiler

She is in love with him but backs down when she realises, after being with Takara in the hospital, that there is no chance for her to win. She is the reason why Takara and Hikaru break up because Takara feels that it is his fault that she was hurt and vows to protect her. She told Takara that she knew he'll leave her one day soon, saying that he can not love her, as he still loves Hikaru. She states that when loving a person, you wish for their happiness, not their person.

Wapedia -Wiki: Moe Kare