This page is about the object. You might be looking for the episode of the same name.

Yui's Heart (ユイの心, Yui no Kokoro?) refers to an item containing the data for Yui's program, which is around three terabytes large.[1] The item is officially known as MHCP001, which stands for Mental Health Counselling Program, by the system.


Yui's Heart is an object which has the appearance of a crystalline water droplet.[2]


Aincrad ArcEdit

Morning Dew GirlEdit

On November 1, 2024, after Yui's existence was detected by the Cardinal System, Kirito utilized a system console in the Hidden Dungeon to search for Yui in the Sword Art Online server with the search command. He then extracted and compressed the program into his own NerveGear's storage, creating Yui's Heart as an object in the game. Asuna then used the item as a necklace.

Fairy DanceEdit

When Kirito first logged into ALfheim Online on January 20, 2025, he noticed that his account shared data with his SAO avatar. He then quickly checked his item storage and, among all his corrupt items, he found Yui's heart. By selecting to materialise the object, the item was taken out of his inventory. Kirito then tapped on the item to activate it and it turned into Yui, the Navigation Pixie.




SAO Weapons Anneal Blade - Dark Repulser - Ebon Dagger - Elucidator - Guilty Thorn - Karakurenai - Lambent Light - Liberator - Mate Chopper - Stout Brand - Sword Breaker - Throwing Pick - Tyrant Dragon - Wind Fleuret
Argyro's Sheet - Blackwyrm Coat - Coat of Midnight - Cor - Crystal Bottle of Kales'Oh - Crystallite Ingot - Crystals - Divine Stone of Returning Soul - Dusk Lizard Hide - Eternal Storage Trinket - Hand Mirror - Mighty Strap of Leather - Mirage Sphere - Pneuma Flower - Potions - Ragout Rabbit's Meat - Ring of Agility - Ring of Angel's Whisper - Scavenge Toad Meat - Tremble Shortcake - Vendor's Carpet - Yui's Heart
ALO Black Iron Great Sword - Blue Long Sword - Crest of Yggdrasil - Demonic Sword Gram - Holy Sword Excalibur - Lightning Hammer Mjölnir - Long Sword - Sap of the World Tree - Yrd
GGO Accuracy International L115A3 - Credit - Defense Field - FN Five-Seven - GE M134 Minigun - Kagemitsu G4 - Metamaterial Optical Camouflage Mantle - PGM Ultima Ratio Hecate II - Plasma Grenade - Procyon SL - Satellite Scan Terminal - Starship Metal Estoc - Type 54 "Black Star"
Project Alicization Black Lily Sword - Blue Rose Sword - Conflagrant Flame Bow - Divine Object - Dragon Bone Axe - Fragrant Olive Sword - Frost Scale Whip - Gigas Cedar - Goblin Sword - Heaven Piercing Sword - Night Sky Sword - Silvery Eternity - Time Piercing Sword - Twin Edged Wings
Community content is available under CC-BY-SA unless otherwise noted.