Isekai Idou Yuukai Yado Kitan Sandou no Torinozu Tei: Sacrifice 1 ~Onna Ninja Hizakura~

In this short story set in a fantasy world of swords and magic,
the venomous fangs of a human trafficker which runs a shady
inn sink deep into the unwitting adventuring party.

His first target... the party's Ninja Girl.

[From DLsite]