Arve Rezzle: Kikaijikake no Yousei-tachi, Mou Hitotsu no Mirai wo. Recommendations
"Arve Rezzle: Mechanized Fairies" / "Arve Rezzle: Kikaijikake no Yousei-tachi" and "Mou Hitotsu no Mirai wo." are short standalone science fiction works that involve an experiment or procedure having unintended consequences and thus resulting in an unfavourable outcome for the protagonists.
These two anime both happen to feature a machine with a tank that the body rests in during its usage as well as a twist that leads up to a cliff-hanger ending.