How did amu get dia?

She just born like Ran, Miki and Suu...
*check out episode 27*

when amu wants to get stronger and shining thêm brightly. she wants to find the answer for believing someone too...

when amu's desire to shine in front of others was made

Amu got Dia just like Ran, Miki,Su.She didn't like the changes in the spring and Dia changed with a "X" mark in her egg.She went to Utau because she had the same feelings wanting to shine.It was hard to get Dia back.But after Amu believing the radaince sleeping inside her,Dia return with her true form.She after went to slumber.She fully reborn in episode 100.

She was born a little while after Ran, Miki and Suu. But soon after she was born, she became an X-Egg, and became Utau's Chara for a while. Then when Amu realised her radiance inside of her, Dia went back to Amu.