|This article is about a/an transformation equipment in Kamen Rider Build.|
The Grease Perfect Kingdom (グリスパーフェクトキングダム Gurisu Pāfekuto Kingudamu) is an adapter based on the Hokuto Three Crows that assists Kazumi Sawatari, complementing his new Grease Fullbottle. Unlike the other transformation devices in the series, which all use some form of Nebula Gas, the Grease Perfect Kingdom uses Phantom Liquid extracted from the Hokuto Three Crows.
Grease Perfect Kingdom has four finishers.
- Stag Slash (スタッグスラッシュ Staggu Surasshu): Grease covers his arm blades in blue energy before slashing the enemy, followed by an X-shaped slash with both blades.
- Owl Attack (オウルアタック Ōru Atakku): Grease flies into the air and rams into the enemy four times in quick succession.
- Castle Break (キャッスルブレイク Kyassuru Bureiku): Grease rotates his shoulder pads forward and charges them with red energy before firing two streams of that same energy.
- Perfect Kingdom Finish (パーフェクトキングダムフィニッシュ Pāfekuto Kingudamu Finisshu): Grease jumps into the air as images of the Owl Hard Smash, Stag Hard Smash, and Castle Hard Smash performing flying kicks appear alongside him. The three images then combine with Grease in the form of yellow, blue, and red chains of energy. The energy converges into a colorful vortex of energy on Grease's foot as he delivers a powerful flying kick to the opponent.
- The order in which the attacks are selected is the same order in which the members of the Hokuto Three Crows died.