Nobody knew Shinobu had a sister.

You had kept your identity hidden from the corps for a long time, in hopes of protecting your sister from questions such as "You have two sisters?" and the inevitable backlash she would face if you were revealed.

You resided in your estate, which you shared with Shinobu outside of the butterfly mansion. Most of the time, you concocted poisons and medicines from wisteria and other things.

Today, Shinobu had invited the male hashiras, and Tanjiro, Zenitsu, and Inosuke over for tea at your shared estate. You didn't know this, but most of the day you remained in your bedroom reading and refining poisons.

But, all of a sudden, you emerge from your room.