A girl who was apprenticed to an old castle rumored as a nest of monsters.
She witnessed "something heteromorphic" which roamed around there.

Although people in the castle call it "komadori", nobody tries to talk details.

Robin, alone, starts investigating the hidden truth, but ……

"It's all right even if it's right. It's all right even if it's wrong."
"If I can choose only one path by which I won't regret, it's for me, ―――"