The Flashback Light, called the Remembering Light (思い出しライト, omoidashi raito) in the original Japanese, is an item featured in Danganronpa V3: Killing Harmony. Its exact origins are uncertain, but it is a device used by Team Danganronpa and The Mastermind of the Killing School Semester to implant false memories into its participants for the purpose of creating an exciting story for the Killing Game. Originally the Flashback Lights were presented as a tool for curing amnesia to goad the participants into using them.
Flashback Lights, regardless of what memories they implant, always appear as a highly advanced flashlight with multiple computer components and wires attached to it. Later on, during a Flashback Light sequence during Chapter 6's investigation, Monokuma uses a Blackout Light to wipe the students' memories of participating in The Gofer Project. Although this memory was fake, a Blackout Light or similar technology was likely used to wipe the participants' memories of auditioning for the Danganronpa TV show before the game's Prologue.
When used on a participant, the world around them is described as "warping" or "twisting". While the Flashback Lights' primary purpose is to implant memories, they can also replace old memories, and memories replaced by the Flashback Light can never be returned.
The Flashback Light was first shown in the Prologue, where everyone was given their "first memory" after they were given their new wardrobe. Upon seeing this Flashback Light, the Prologue seemingly starts over, but this time everyone remembers that they are Ultimate students.
The Flashback Light made its next appearance in Chapter 2, hiding within a large treasure chest on the second floor of the academy. It was found by Shuichi Saihara and Angie Yonaga, but the latter promptly took it after Shuichi refused to turn it on. Everyone later gathered in the gym where, after thinking about it once more and with Monokuma's encouragement, they decided to use the Flashback Light. Upon using it, everyone remembered that they had been on the run from the Ultimate Hunt, and that they had discarded their talents to live as normal high school students, concerning the participants.
The Flashback Light returned in Chapter 3, where it was found in the computer room on the fourth floor of the academy. Kokichi took the Flashback Light once Shuichi discovered it, and the participants used it in the dining hall, supposedly remembering their own funeral.
Once again, the Flashback Light returned in Chapter 4; this time, upon using it, everyone remembered the meteorites impacting Earth, as well as the The Gofer Project, the project set up in order to preserve humanity.
The Flashback Light made its final, but arguably most major, appearance in Chapter 5. After Kokichi Oma convinced everyone that he is the mastermind and that the Earth, including every living person on it, is dead because of the meteorites, everyone fell into despair so much that they have no drive to continue the killing game any longer. The Mastermind, however, prepared a Flashback Light and left it in the dining hall for the participants to discover. Once used, everyone barring Kokichi and Kaito Momota who were still inside the Exisal hangar, remembered that they were actually students of Hope's Peak Academy. They remembered everything about The Tragedy, Junko Enoshima, and that they themselves were symbols of hope. With this newfound determination, everyone prepared to fight Kokichi and save Kaito.
During Chapter 6's investigation, Shuichi located something odd on Classroom C on the second floor of the school: a device used to create Flashback Lights. It is here that he found out that the contents of the memories stored within the Flashback Lights were selected, and the Light itself, once completed, forms in the nearby locker. Once Himiko Yumeno entered the room, the device seemingly shut off and the whole classroom returned to normal. During the final Class Trial itself, Shuichi finds out that everything that they had remembered from the Flashback Lights had been nothing more than lies, which were acknowledged by Tsumugi and Monokuma, essentially meaning that everything from the Flashback Lights never mattered at all.
While the Flashback Light is circle-shaped and green, the Blackout Light is square-shaped and red.