The following describes the truth of what happened behind-the-scenes in Banquet of the Golden Witch.

Culprit: Sayo Yasuda and Eva Ushiromiya as separate killers, without Sayo knowing Eva's involvement until near the end.

Accomplices: Terumasa Nanjo (Sayo's), Hideyoshi Ushiromiya (Eva's).

Before the murders: Sayo played the witch's part and gave Maria the letter.

The first twilight: Sayo killed Genji, Kumasawa and Gohda. She constructed the closed-room ring with them, Kinzo's corpse and dressing as both Shannon and Kanon. The first corpse found was Shannon's. Then, after everyone went away, she quickly dressed as Kanon, the last corpse. She locked the chapel from the inside and played dead as Kanon. By killing both Shannon and Kanon personas, "none of the murders were suicides, traps or accidents."

It is however never said in red that the last three rooms, including the chapel, were locked.

"Illusions to illusions. In the closed-room ring, the end and the beginning overlap." - Willard H. Wright

After that, Eva solved the epitaph and discovered the gold. When Eva was returning to the mansion, she met Rosa (who also solved the epitaph). They talked about sharing the gold, but Eva wanted to keep it all for herself.

The second twilight: Later, Rosa and Maria went to the garden and met Eva. Eva and Rosa disputed about the gold. The dispute turned into a full-blown fight, and Eva struck Rosa, causing her to fall over and stab herself on the metal thorn of the fence. Rosa died. Eva, turning around and seeing Maria's look of horror at Eva's having killed her mother, grabbed Maria and strangled her to death. She then sneakily made her way back to the room Hideyoshi was in, making sure not to be spotted by anyone else.

The fact Hideyoshi was smoking and covering Eva, proves she had intended to kill Rosa as soon as she left the room, and talked to Hideyoshi about it.

The fact this follows the epitaph is a coincidence, however the bodies were not pierced by stakes, hinting at it.

"Earth to earth. No falsehoods in their final moments as told." - Willard H. Wright

The fourth twilight, fifth, and sixth twilights: Rudolf and Kyrie suspected Eva thanks to the cigarette left in the room Hideyoshi and Eva were supposedly in, and planned to corner her. Rudolf and Kyrie dragged Eva and Hideyoshi to the main mansion with the fake premise of getting more food (presumably not to put the kids in danger if things went wrong in the guesthouse). When confronting them, Eva and Hideyoshi shot both Rudolf and Kyrie. However, before dying, Kyrie used her last strength to shoot Hideyoshi.

To make it look like it had been the work of the witch, or the same person who carried the first twilight, she grabbed three of the stakes that had been used for the first twilight and placed them on the bodies. The fact the three gunshot body spots matched the first three twilights, was a coincidence.

Another interpretation is that Sayo was nearby and saw the scene. After Eva left, she placed the stakes on the three bodies. However if this were the case, Eva would've potentially reacted to the stakes more when she came back with the others.

"Earth to earth. No falsehoods in their final moments as told." - Willard H. Wright

The seventh and eighth twilights: When Eva returned to the guesthouse alone, Krauss and Natsuhi were asleep, as she had sedated their coffees. She strangled them with a rope, moved their corpses outside the mansion, and locked the guesthouse.

Her intention was to clear away suspicion from her, and eventually kill everyone but George, however making it look as if it hadn't been her work, so George wouldn't suspect her and they could keep all the gold.

"Earth to earth. The obvious culprit wields a mutable blade." - Willard H. Wright

The ninth twilight: Sayo called Nanjo by telephone and ordered him to tell George she was alive (thankfully nobody heard the phone ringing and she called the room Nanjo was staying in). When George arrived where she was "dead", Sayo was pointing a gun at him and killed him. It can be assumed that by this point she'd realized deaths had occurred, which is why Sayo's next twilight after the first was not the second and instead jumped to a single death twilight. However the reason why she didn't pierce George's body with a stake is not known.

The reason why the bank PIN (07151129) was left on the door is also unknown, especially given you also need a card, and certainly instructions, to use it, but it could simply be to strengthen the mystery aspect.

When they find George's body, Shannon's body is not there, however they fail to notice it.

Jessica incriminated Eva and was blinded by accident when Eva's gun almost shot her in the face. Nanjo took care of her, while Battler was looking over Eva. Sayo then killed Nanjo, shooting him in the head. This makes an extra victim that dies before the tenth twilight, according to the epitaph, but this is because Sayo was unaware of the total number of people Eva had killed. Sayo then played Kanon's role (however Kanon's death had already been acknowledged and would soon be again by EVA-Beatrice, so it was not the full Kanon persona resurrecting), telling Jessica not to touch him (because she would realize that "Kanon" was dressed as Beatrice, since that's what she does once both Kanon and Shannon are dead) and moving Jessica to another room. Finally alone with Battler, Eva killed him by shooting through his heart, even though the reason why she didn't simply shoot all of them once she found George dead is questionable.

The tenth twilight: Sayo hid Jessica behind a curtain, but was shortly spotted by Eva. Eva, upon seeing Beatrice, claimed and proved to have solved the epitaph, as to which Sayo was unaware of. Beatrice told Eva about the bomb, and about how to escape the explosion by going to Kuwadorian. Eva followed the instructions and was saved. The bomb killed Jessica, and Sayo was either killed by the bomb or Eva.

Why she chose to save Eva only, and not Jessica too by deactivating the bomb altogether or telling Eva to do so instead, is unknown, since that's what would be done according to her rules once somebody solved the epitaph.