Hairu accidentally built a shelf

I was previously unaware of this phenomenon. Many thanks for enlightening me. 

Matsumae dodges another blast from the investigator’s quinque. Wow, she is good.

And not even Shuu’s age. 

“Look out.” Ihei Hairu aims again for her kagune shield, but just then, she slips on a patch of spilled blood.

Before Matsumae can slice her through the abdomen, Hairu has tumbled into her kagune shield. It wavers for a moment, then reforms as a shelf.

“Hah?” Matsumae stops their fight to stare.

“First Class! Do you need help?!” Two subordinates approach.  

“Help? I accidentally built a shelf,” Hairu calls back. She grins at the ghoul. “Of all the imposing shapes, that is not one of them.”

“I didn’t do it on purpose,” snaps Matsumae.

“I don’t want a shelf quinque. Or one with a mind of its own.” Hairu frowns. “I’m not sure I can break through.”

“I’m not sure I can change it back,” Matsumae replies. Her kagune is stubborn today. “Call it a draw, then, young one?”

“I’ll kill you later,” Hairu calls as Matsumae detaches herself from the kagune and flees.