- "The hope you entrusted to me, I will make sure it comes true."
—An in the manga Chapter 24
Rizuna An is a character first appears in the Beach arc. A woman who is trusted for her wisdom in solving the difficult puzzles in the games.
Not much is told about her past before entering the Borderland except that she was a forensic officer in the police department, specialized in fingerprint analysis. She is the very first few players convinced by Boshiya to establish his utopia, the Beach. When the Beach society is divided into 2 sects, An is seemingly following Boshiya's "idealistic sect", instead of Aguni's.
In her debut game, the Four of Diamonds, An calmly comes up with a perfect solution when all 3 of her teammates panicking because of imminent death. When Witch-Hunt begins and Aguni ruthlessly orders the members of his martial sect to kill all Beach residents, An is looking for superglue which contains cyanoacrylate to help bake the murdering knife for fingerprints. Her close friend is killed by Last Boss but Kuina defends for her, buying her time to escape to a room with required equipment. The fingerprints on the knife handle show that the knife was carried in the opposite direction, which means the "Witch" used it for suicide, not homicide. Before An can reveal the truth of Witch-Hunt, she is hit in the head, but luckily the wound is not fatal and she is not thrown into the bonfire. Just before the game is about to end, An is carried by Mahiru to Aguni and verify Arisu's deduction of the Witch's identity.
When the Beach resort is destroyed in fire, An with her 2 Beach fellows have successfully challenged the Queen of Diamonds in the first day of the second stage. After that they simply hide until only the Queen of Hearts game remains, An heads towards the last arena and reunites with her former allies. She also volunteers to be the pioneer of the last game, but loses at rock-paper-scissors to Arisu and Usagi.