Busou Shinki Moon Angel

Masato is a high school student who has been living abroad and has now returned to Japan. On his first day of school, he is awoken by An, his Arnval model Shinki. As he hurriedly prepares to depart, Aines, an Altines model, and Lene, an Altlene model, both make their way out from the boxes they had been packed within.

For the sake of their Master, they enthusiastically go about cleaning and squaring away Masato's belongings. In the midst of this, they come across a box labeled "Valuable".

What could be inside?