The twenty fourth chapter of the Darwin's Game ~Flag Game~ novel.
All of the doubts and mysteries that the Sunset Ravens had encountered so far assembled themselves in Rein's mind and revealed the truth. Rein announced that she'd finally figured it out, prompting Kaname to ask if it was about Wadatsumi's betrayal, which she confirmed but also added that the most important part was the two Kaji. Ryuuji apologized for not being able to see through Kaji's lie at the warehouse, though Rein corrected him, telling him that he did see through "Kaji's" lie. However, both Kaname and Ryuuji didn't believe her, pointing out that a message had been sent from Kaji's account and that players couldn't use other players' accounts. Rein agreed that it normally wouldn't be possible, then mentioned that "Kaji", or Fuli, most likely had a privilege like Kaname did.
At first, Kaname was bewildered by Rein's answer, but then gradually realized the truth. Despite this, the others didn't understand what Rein was getting at, causing Ximing to suggest that Rein should start from the beginning. Rein explained that the reason she went on a reconnaissance mission to the Black Lotus base was because she'd received information that an elderly man named Fuli had recently joined.
Although she didn't get any useful information, she confirmed that the Kaji that came to negotiate the deal was the real Kaji, or Kaji A. Fuli took advantage of Kaji's trust and the pro and anti-alliance split within the clan to suggest the weapons deal to him, and later killed Kaji in the warehouse, taking his place as Kaji B. She finished her explanation by saying that the situation behind Wadatsumi was the same as Kaji.
Ryuuji was satisfied by her explanation, nevertheless he pointed out that it didn't explain how Fuli was able to send a message through Kaji's account, and Shuka pointed out that there was no way the clans wouldn't figure out Fuli's treachery since control of a clan would move to the vice leader or below upon the leader's death. Their points were something that previously prevented Rein from solving the mystery, but then she learned that Shuka's father had been killed outside of the game, causing her to come up with the theory that Fuli was an executioner that worked for the Game Master.
There had been rumors that there were executioners who carried out the Darwin's Game management's orders such as murdering rule breakers or those that attempted to research the game. In addition, there was another rumor that these executioners were former players who were scouted, and in exchange for their services they were given a privilege. At that point, both Shuka and Sui realized what Rein was getting at, but Ryuuji still didn't understand. Hearing this, Rein explained to him that Fuli had a privilege that allowed him to take over player accounts.