If You Do Not Behead, You Cannot Understand summary:

The fourth year of the Meiji Era. Yukinosuke, the son of a family of the privileged aristocratic class, goes about his life covering up a worry he has, being “I have not once had an erection”. In the midst of such troubled days, he meets Sayo, the head of a family of executioners spanning back into the Edo period. After witnessing a beheading performed by her, something pitch black starts to well up inside Yukinosuke!! Sprouting from lust begins a noble romance of blood and nature!!