Disclaimer: I always forget to put this, but I do not own either Okami or MLP:FiM, although if I did, I'd burst into flames of happiness.
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Amaterasu was awoken by her son, Chibiterasu, eager to help her start the day by rising the sun.

Celestia was awoken by her younger sister, Luna. The night was over and Celestia had to raise the sun to start the day.

Amaterasu stood side by side with her son, and with a howl rose the sun.

Celestia flew into the sky and used her magic to raise the sun.

Chibiterasu smiled and his mother smiled proudly at him.

Luna grinned at her older sister, and went to her room to fall asleep and await the time to raise the moon.

Two sun goddesses, much in common, but from very different worlds.