Guide
How the kit works
Start with Salon Solitaire in Ousia. It deals AoE Hydro damage and summons three Salon Members, who attack nearby opponents at intervals. Their damage scales with Furina's Max HP. They prioritize the active character's target, so you can direct their attacks by choosing whom to fight.
Use Let the People Rejoice, then let the party's HP rise and fall. Each percentage point of Max HP gained or lost by a nearby party member gives Furina one Fanfare. Fanfare increases nearby party members' damage and Incoming Healing Bonus; it is cleared when the Burst ends.
The Salon Members consume HP from nearby characters above 50% HP when they attack. With one, two, three or four qualifying characters, their attack deals 110%, 120%, 130% or 140% of its original damage. A healer can restore that HP and produce more changes for Fanfare.
Use the Charged Attack from Soloist's Solicitation (NA) to switch Arkhe alignment. Pneuma replaces the attackers with the Singer of Many Waters, who heals nearby active characters at intervals. Switching back restores the attackers, but the new guests inherit the remaining duration rather than starting a fresh one. Furina starts in Ousia when she takes the field.
Build and why
Use four pieces of Golden Troupe for the attacking guests. The set increases Elemental Skill damage by 20% with two pieces and by another 25% with four; it adds a further 25% while Furina is off-field. As alternatives, combine two pieces of Golden Troupe with two of Tenacity of the Millelith for HP, or with two of Emblem of Severed Fate for Energy Recharge.
Four pieces of Tenacity of the Millelith are an option when the team wants its 20% ATK bonus and 30% Shield Strength bonus after Skill hits. Scroll of the Hero of Cinder City is another support option: an elemental reaction involving Furina's element can give the team an Elemental DMG Bonus for the elements involved.
Choose Energy Recharge or HP Percentage on the sands, HP Percentage or Hydro DMG Bonus on the goblet, and CRIT Rate, CRIT DMG or HP Percentage on the circlet. For substats, look for Energy Recharge first, then HP Percentage and CRIT. Max HP helps both guest damage and healing; Energy Recharge helps get the Burst back.
Splendor of Tranquil Waters is the first weapon choice: HP changes can increase Skill damage and Furina's Max HP, even while she is off-field. Favonius Sword is a useful energy option, with CRIT hits having a chance to generate particles. Key of Khaj-Nisut gives HP and can share Elemental Mastery with nearby teammates after its Skill-hit stacks are built.
Leveling priority
I suggest leveling Salon Solitaire first for the guests, then Let the People Rejoice for its team bonus. Leave Soloist's Solicitation (NA) until last in the usual off-field build, where Furina mainly uses its Charged Attack to change alignment.
For ascension, gather Lakelight Lily, Water That Failed To Transcend and the Varunada Lazurite materials. You also need Whopperflower Nectar, Shimmering Nectar, Energy Nectar and Mora.
Talent upgrades use Teachings of Justice, Guide to Justice and Philosophies of Justice, along with the same Nectar materials and Mora. Lightless Mass is needed too, and each talent taken to its maximum requires a Crown of Insight.
Constellations worth it
For constellations, C2 and C1 are the first upgrades I would consider. C1 gives Furina 150 Fanfare when she uses her Burst and raises the limit by 100. It gives the team a head start on the bonus rather than waiting for HP changes to build every point.
C2 increases Fanfare gained from HP changes by 250% during the Burst. Points gained above the limit also increase Furina's Max HP, up to 140%, helping the HP-based parts of her kit. It requires C1 first.
C6 is worth considering for a different way to play on-field. After the Skill, Furina's attacks become Hydro damage for up to 10 seconds and gain damage based on her Max HP. In Ousia, qualifying hits can heal nearby party members; in Pneuma, they gain more damage and consume party HP. The effects can trigger up to six times per use.
C3 raises the Burst's level, C4 restores Energy through the guests, and C5 raises the Skill's level. They are useful steps, but you can skip pursuing them if you are happy with the base kit. None is needed for the off-field setup.
Teams
Look for a damage dealer who can use Furina's team damage bonus and a healer who can restore HP spent by the guests. Healing several party members is especially helpful for keeping more characters above the guests' 50% threshold and creating HP changes for Fanfare.
Xilonen and Xianyun are healer options. Neuvillette is a Hydro teammate with healing, while Kaedehara Kazuha offers an Anemo slot associated with Swirl. One team to consider is Furina, Neuvillette, Xilonen and Kaedehara Kazuha.
Yelan or Xingqiu can fill another Hydro slot if you want an off-field teammate. Furina's guests provide Hydro attacks while the active character fights, and her Burst rewards HP changes across nearby party members rather than changes to Furina alone.
Common mistakes
Do not leave the team without a healing plan just because Furina has a healing mode. The Singer replaces the attacking guests, so staying in Pneuma means giving up their attacks for as long as the Singer is present.
Watch the party's HP instead of expecting the guests to keep their stronger attacks when everyone is low. Only nearby characters above 50% HP count toward the attack increase and have HP consumed by those attacks.
Do not switch guest types expecting a fresh duration. Recast the Skill when needed instead. Also avoid building only HP at the expense of Energy Recharge: the Burst needs to be available if you want its Fanfare bonus during the fight.
