Mala Suerte!3 "Monstruo Sangriento"

As Ichigo and Rukia brace against Grimmjow's staggering pressure, the Espada lands nearby and asks which of them is stronger. Before Rukia can pull Ichigo back, Grimmjow drives his hand through her midsection, remarks that she is not the one, and casts her aside as Ichigo charges in fury. Across town, Edrad lectures Ikkaku that an Arrancar's sword is sealed within the body itself, so releasing it unlocks both true power and true shape, and that Volcánica is now his real strength. He looses a blast of flame that sends Ikkaku hurtling through several blocks.

Watching the one-sided beating, Yumichika calmly phones the Research Institute to request a wide spatial freeze around Ikkaku, citing the enemy's unexpected power and civilian safety, and extends the same request to the fights of Hitsugaya, Rangiku, Renji, Rukia, and Ichigo, coldly adding that a funeral should be readied for Ikkaku too. Edrad hammers Ikkaku through a building and roars with delight at his released might, until Ikkaku halts his fall with Hoho and releases his Shikai, Hozukimaru. A flaming punch shatters the weapon and sets him ablaze. Told to surrender, Ikkaku only grins, and when Edrad's fist comes down in a pillar of fire, the smoke clears on a bloodied Ikkaku bracing the blow with his back. Lamenting the gap between them and hoping the others are too busy to see, he tells Edrad to watch closely and keep quiet, then triggers his Bankai.

Part of Volume 23, MALA SUERTE!, in the Arrancar arc, and adapted into Episode 118, Ikkaku's Bankai! The Power that Breaks Everything. The Spanish subtitle Monstruo Sangriento translates as Bloodstained Monster. This is the chapter where Ikkaku, cornered by Volcánica, finally reveals that he can perform Bankai.