From Sherbet Lemon:

Moon God Calendar Year 2075, Olandier Palace given out an urgent imperial verdict to summon the whole nation's young nobility into the palace. From the flourishing Didaosidin to the distant border plains. Regardless of how faraway the confer territory are, all Young nobility age from 10 to 16, must rush to the palace immediately. On the surface, they are choosing the future supports for the country, but its only a pretext to conceal a sinister conspiracy.

This is the prologue series that leads to the main series "Tree of Moonlight" It's the beginning of the story and introduction to the characters.