Yuuenkatsu, (大調和, lit. Grand Harmony) is Kaito's zanpakuto. It has an oblong guard and a long red sheath. The guard has a Yin-Yang engraved on it. He wears it on his waist. Yuuenkatsu's release command is "Conduct the Heavenly Opera". The spirit of Yuuenkatsu is that of an angelic being of yellow energy, that uses a harp. This being does not actually attack in battle.
- Shikai: In its Shikai, Yuenkatsu's sheath and guard turn black, and it loses a tassel.
- Shikai Special Ability: His shikai , when activated, has an instant release effect. It releases a continuous series of vibrations that disrupt the enemy's heart beat, causing them to tire 25% faster.
- Kaonpuo Seishukukaidan (美しい音楽サイレントの階段で, ( Beautiful Music on Silent Stairway: Crescendo )
This move causes the blade of Yuuenkatsu to vibrate rapidly. This ensures that the strike of this blade can create fissures in the ground if struck, and weaken structures or metallic objects.
- Tomokenzanme Tenraikangen ( 全能の神の音楽のアイ, ( All-Seeing Eye of Divine Music : Largo )
This move performs a sort of "echolocation" allowing the user to sense invisible, hidden, or fast enemies.
- Seikouta Umoushinteki ( 絶妙な歌の子孫は、物理的に, ( Exquisite Song Descends to the Physical )
This allows the sword to cause any particles upto two miles away to vibrate. This could cause the object to heat up, or user could slow down the vibrations to make an object cool - also, if certain objects are vibrated, they could produce shrieks if sound to disorient, or bursts of static electricity.
- Bankai: Teikoku Yuuenkatsu (帝国大調和, Imperial Grand Harmony) causes the sword to transform into a broad bladed short sword, with a Yin-Yang on its hilt and intricate carvings along the blade.
- Bankai Special Ability: He has several Bankai techniques:
- Gyakusetsukashou (パラドックスソング, Paradox Song):
This technique can only be performed after the zanpakutou has already had a "taste" of a particular energy based technique. The sword then vibrates at the opposite frequency, effectively cancelling the attack.
- Setsudankashou ( 切断ソング, Disconnection Song):
This technique causes the blade of Yuuenkatsu to vibrate at the exact opposite frequency of the opponent's Reiatsu, preventing them from accessing it properly.
- Nimen no Ongaku' (音楽の2つの顔, Two Faces of Music):
This technique is the most powerful move of Teikoku Yuuenkatsu. It causes a lullaby to occur, causing the opponent to become entranced and drop his guard. Then, without warning, a fusillade of bullets of condensed sound strike the opponent, each with a harsh, disorienting impact.