Hēiàn Yǐnrú

"But you remained. With no regard for your own safety, you returned to Las Noches to fight. Because you are Seijin. We have absolute faith in the unshakable determination of the Shinigami heart. The Shinigami with the most exceptional drive and will, henceforth the Seijin, are who we chose for our sacrifices."

- Hēiàn Yǐnrú to Seireitou Kawahiru

Hēiàn Yǐnrú (黑暗隱孺, Yīnrū Hēiān) is an Arrancar in Akujin's Arrancar Army, and holds the title of Cero (0). He is seen as the youngest of the Arrancar, being of child age. It was explained that Hēiàn was born from the Ōin's power, by using genetic material from Sora.

Trivia

 * Hēiàn (隱孺) means "Darkness"
 * Yǐnrú (黑暗) means "Hidden Child"
 * Hēiàn's appearance was based on Homunculus Pride from Fullmetal Alchemist