Okay, I see many people were asking this, "unlock Aya shower scene?" Although I didn't play this game, however I had the answer here. (video included)
Aya Brea's shower scene (Caution: partial nudity!)
How to unlock:
Defeat all of the Land & Flying Twisted (歩行型ツイステッド / 浮遊型ツイステッド) appear in this episode.
Defeat all Flying Twisted that will release poison gas, receive Search Record.
Pick up all item available in this episode, receive Search Record.
Withdraw supports to receive Search Record. Following by killing the enemies of BABEL in the helicopter. As long as killed those who're attempt to attack the soldiers.
Any requirement above that is undone during the playthrough can be redo again in the Case Training.
There are no Aya Brea shower scenes to unlock in episodes 0, 5, and the Last EP.
The info above is translate from THIS SITE, I hope if anyone knows Japanese better or find any info should make correction, please give me a note.