When Luna, Shingo, Bell, Chako, and Menori accidentally stumbled onto the strange building and entered, they found a strange young alien boy in a cryogenic sleep. Upon awakening, Luna found the boy's name was Alduram Gyet and that she was to take care of him. It wasn't until Howard blurted out the name Adam, that he was given the nickname. It's unclear how he got there or why, but Luna and the other plan to find out.

Info taken from Wikipedia