A Lamia named Echidna captured two maids from a mansion who trespassed upon her dungeon after sending a death threat to the mansion. After crudely violating the maid pair they were eventually transformed into mermaid monster girls and imbued with unbelievable power and sent back to the mansion.

You are the master of the mansion who now ponders why do those punctual maids of yours are suddenly late..but think nothing of it. Then you notice your maid twins returned home and nothing seemed to be amiss about them. "We've arrived, Master! Do excuse our tardiness!" one of the maids said.