Guide
How the kit works
Start by using Sanctifying Ring. It costs part of Kuki Shinobu's HP and deals Electro damage nearby. The Grass Ring of Sanctification then follows the active character, dealing Electro damage every 1.5 seconds and healing active characters in its area based on Kuki Shinobu's Max HP. The skill's HP cost cannot take her below 20% HP.
Switch to the teammate you want on the field and stay close enough to opponents for the ring to hit. Return to Kuki Shinobu when you need to use the skill again. Her Elemental Mastery also improves the ring: its healing increases by 75% of her Elemental Mastery, and its damage by 25%.
Use Gyoei Narukami Kariyama Rite when you want its field to deal continuous Electro damage. The damage is based on Kuki Shinobu's Max HP, and the field lasts longer if she has 50% HP or less when she casts it. At that same HP threshold, her Healing Bonus increases by 15%. The longer field is useful, but don't ignore the risk of keeping her at low HP.
Shinobu's Shadowsword (NA) gives her normal, charged and plunging attacks. You can use them when needed, but the ring keeps working while another character is active.
Build and why
For Hyperbloom, start with four pieces of Flower of Paradise Lost. Its two-piece effect gives 80 Elemental Mastery, and its four-piece effect increases the wearer's Hyperbloom damage. The effect can also be triggered while the wearer is off-field.
Four pieces of Gilded Dreams are another option: the set gives 80 Elemental Mastery and can grant more after a reaction, depending on the elements of the other party members. For a team-support build, four pieces of Tenacity of the Millelith give 20% HP and increase nearby party members' ATK by 20% and Shield Strength by 30% for 3 seconds when the skill hits.
Use Elemental Mastery on the sands, goblet and circlet for Hyperbloom. HP Percentage is an alternative on each piece, while Healing Bonus is an option on the circlet if you need more healing. For substats, look for Elemental Mastery first, then HP Percentage, Energy Recharge and HP.
Freedom-Sworn is the first weapon choice in the guide evidence. It increases damage by 10% and gains Sigils when its wielder triggers reactions, even off-field. Xiphos' Moonlight gives the wielder Energy Recharge based on Elemental Mastery and shares part of that buff with nearby teammates. Iron Sting gains damage bonuses when its wielder deals Elemental DMG.
Key of Khaj-Nisut is another option for healing and team support. It increases HP by 20%; skill hits build an Elemental Mastery bonus for the wielder, and three stacks also grant nearby teammates Elemental Mastery based on the wielder's Max HP.
Leveling priority
A sensible talent order is Sanctifying Ring first for the healing and damage you use most often, then Gyoei Narukami Kariyama Rite for its field damage. Leave Shinobu's Shadowsword (NA) until last if you mostly keep Kuki Shinobu off-field.
For maximum ascension, gather 420,000 Mora, 168 Naku Weed, 1 Vajrada Amethyst Sliver, 9 Vajrada Amethyst Fragment, 9 Vajrada Amethyst Chunk, 6 Vajrada Amethyst Gemstone, 18 Spectral Husk, 30 Spectral Heart, 36 Spectral Nucleus and 46 Runic Fang.
To fully level all three talents, you need 4,957,500 Mora, 3 Crown of Insight, 9 Teachings of Elegance, 63 Guide to Elegance, 114 Philosophies of Elegance, 18 Spectral Husk, 66 Spectral Heart, 93 Spectral Nucleus and 18 Tears of the Calamitous God.
Constellations worth it
To Sever Sealing is the standout upgrade in the guide evidence. When a character protected by the ring hits with a Normal, Charged or Plunging Attack, it drops a Thundergrass Mark that deals AoE Electro damage based on 9.7% of Kuki Shinobu's Max HP. It can happen once every 5 seconds.
To Forsake Fortune is worth considering for the extra 3 seconds on the ring. To Ward Weakness can save Kuki Shinobu from a lethal hit once every 60 seconds; dropping below 25% HP also gives her 150 Elemental Mastery for 15 seconds, once every 60 seconds.
To Sequester Sorrow adds three levels to the skill and is useful if you want more from the ring. You can leave To Cloister Compassion and To Cease Courtesies aside if you care more about the ring: they improve the Burst's area and level instead.
Teams
For Hyperbloom, try Nahida as the Dendro teammate and Xingqiu or Yelan as the Hydro teammate. Kuki Shinobu supplies Electro and healing through her ring, leaving another character free to stay on the field. Alhaitham is another Dendro option if you want him on-field.
Yaoyao is a Dendro healer you can consider when you want another source of healing. Outside Hyperbloom, Fischl is an off-field Electro option, while Kaedehara Kazuha brings Anemo and Swirl. Pick the remaining slots for the reactions and support your team needs.
Common mistakes
Don't expect the ring to heal every teammate at once. Its healing reaches active characters within its area, so switch to the character who needs healing. Keep the active character near opponents if you also want the ring's Electro hits to connect.
Don't spend Kuki Shinobu's HP without watching her health. The skill's cost stops at 20% HP, but that does not make her safe from incoming damage. The longer Burst field at low HP is not a reason to ignore a dangerous attack.
Don't copy a full Elemental Mastery build without checking your healing needs. Use HP Percentage or Healing Bonus where needed, and choose Tenacity of the Millelith if its team buffs suit your setup better than the Hyperbloom set.