How Did I, the Mole, Become Their Pet?

Transmigrating into a defeated, captured, totally useless Demon King, and about to be dragged off to be sacrificed as a battle standard?

Charles isn't worried at all: he can create alternate identities and transform himself to save his own life.

To deal with a party of heroes who are all overpowered heroines, he turns into a cute, soft-spoken succubus captive and undermines them from within.

When facing the princess who has imprisoned and confined his real body, he becomes a cool, merciless big-sisterly nun and plays along with her.

Though his spy plan is succeeding step by step, as he watches the girls draw closer to his doubles, Charles can't help feeling that something is off.

"Heh heh heh, you only surrendered because I had you all completely fooled, right?"

"...Right?"