Mahiru Koizumi earned the title of Ultimate Photographer. Raised in a single-parent household by a frequently absent photojournalist mother, she developed a strong sense of responsibility and traditional values. Mahiru often expected chivalrous behavior from male peers and exhibited a protective, sometimes scolding, "big sister" demeanor toward classmates. She firmly believed in justice, fairness, hard work, and honesty. Initially distrustful and critical within the group setting of Jabberwock Island, Mahiru gradually formed bonds, particularly a close, protective friendship with Hiyoko Saionji. Her protective instinct extended to others she perceived as vulnerable. Mahiru valued photography as a means to capture moments of truth and everyday happiness, preserving important memories and connections. During The Tragedy, Mahiru was brainwashed by Junko Enoshima into Ultimate Despair, participating in widespread destruction and chaos. Afterward, she entered the Neo World Program for rehabilitation. Within its simulated killing game, Mahiru died in Chapter 2 during an investigation into the Twilight Syndrome Murder Case—a past Hope's Peak Academy incident involving her, Fuyuhiko Kuzuryu, Peko Pekoyama, Sato, and Natsumi Kuzuryu. Mahiru had photographed Sato killing Natsumi; Fuyuhiko later manipulated events to avenge his sister, leading to Sato’s death and Mahiru’s murder by Peko acting on Fuyuhiko’s unspoken will. Post-program, Mahiru’s consciousness was restored from backup data during the shutdown sequence. In the Hope Arc, freed from Ultimate Despair’s influence, she appeared alongside other survivors to confront active remnants of despair. After the final battle’s resolution, Mahiru joined her classmates in focusing on rebuilding and fostering hope.