Was Natsuki's first love, Atri? His beautiful childhood memories are gradually being overwritten. Despite his unwillingness to admit it was her the facts around him are lining up to force him to, but he continues to deny it. 

Natsuki happens to see Atri's log that was left open. What was written there was an emotionless record of how she carried out her actions to fulfill Natsuki's desires. Natsuki instinctively rejects Atri and is no longer able to trust anything. Meanwhile, a single letter arrives, and inside there is a report describing the truth behind the Humanoid called Atri.