そしてこの宇宙にきらめく君の詩

On a world completely different from Earth people have been living in artificial space colonies for a long time.
A few colonies have gathered together to assemble a nation, the people call it "St. Folia".

The protagonist Lumina is the princess of the Shumal Kingdom that governs St. Folia.

Their power that once spanned the entirety of St. Folia is fading. The Shumal Kingdom's outlying principalities are in a state where they can't sustain themselves without help. With conflicts over the succession of princes and wars between different ethnic groups going on all the time the people are exhausted.
But Lumina knows nothing of that reality, she is growing up sheltered in her own little pure world.

One day it is decided that Lumina will be engaged to a influential prince, the ruler of "Ibleland" Laios.
Lumina opposed the one-sided decision of her father and snuck out of the palace. There she learned that the world is completely different than the one she had been taught about up till now and she was shocked.

"I want to know the real world. I don't want to be a person who doesn't know anything about important people."

Facing the opposition of her father, Lumina goes on a journey to explore the world.
With the company of her childhood friend Ashe who is the kingdom's best swordsman, and her young genius boy tutor Pelmo, Lumina's adventure begins.

official site