Suzu Taniguchi/Chronology

Background
During her childhood, Suzu was constantly lonely due to her parents being too busy with work to spend time with her. After being told to smile by her caretaker Umeko, Suzu crafted her cheerful and upbeat persona in order to get closer with her parents, as well as a way to make friends, but is still depressed deep down. Among those she befriended throughout her youth was Eri Nakamura, who she considered to be her best friend.

Main Series Timeline
One day during her second year of high school, Suzu and her entire class was summoned to Tortus by its god Ehit in order to help humanity's war against the demons. She and her classmates trained in the Heiligh Kingdom for two weeks, under the supervision of Knight Commander Meld Loggins, before they traveled to the Great Orcus Labyrinth, in order to fight the monsters that dwelled inside it until they were strong enough to fight the demons. During their first trip the the Labyrinth, they were all transported to the 65th floor due to a trap that was accidentally set off by Daisuke Hiyama. It was there that they were all surrounded by an army of skeletal Traum Soldiers on one side, and a Behemoth on the other. After a fierce battle, almost everyone managed to escape, but Ayako's classmate Hajime Nagumo was believed to have been killed when he fell off the bridge the Behemoth stood on, after he helped keep it at bay in order for the rest of his class to escape. This ordeal had severely effected the remaining students' morale, but Suzu was among those who resumed their training in the Great Orcus Labyrinth.

When Suzu and her classmates returned to Japan, she planned to tell Eri's mother about her death. However, Eri's mother had moved away prior to the return of her daughter's class. With Hajime's help, Suzu learned about the abuse Eri suffered from her mother. As a result, she became so angry at her that she didn’t even bother to find her and let her know her daughter had died. Instead, Suzu decided to build a grave for Eri in her family's cemetery plot, which she visits every year on Eri’s birthday. She also goes to visit whenever something important happens in her life to fill her best friend in on the details.