Wall Sina, Goodbye: Part Two

Wall Sina, Goodbye: Part Two (Wall Sina, Goodbye (後編)) is the seventh OVA, Episode 16.5B, of the Attack on Titan anime. It was produced by Wit Studio and Production I.G. It is a continuation of Wall Sina, Goodbye: Part One.

Both episodes are anime adaptations of the spin-off manga Attack on Titan: Lost Girls, written and illustrated by Ryōsuke Fuji, and based in turn on the visual novel Wall Sina, Goodbye, by Hiroshi Seko.

The episode was released in Japan with the special edition of Volume 25 of the manga.

Waste Liquid Tank
''A large tank that stores dirty water and waste liquid containing toxic pollutants generated from industrial activities. It has a capacity of 5000m.''

When the dirty water and waste liquid exceeds a set level, part of its content will be transferred to another tank and purified through a special filtration device to make it harmless to the human body before being discharged from the plant.