Wakaba

One of the students in the classroom that was caught in the explosion from the fight between the Demon Lord and Hero at the beginning of the story.

Description
According to references from her classmates, Wakaba Hiiro was the "queen" of their school in terms of beauty. Due to this, she ends up a bit isolated and many people found it difficult to talk to her. She was loner both inside of class and outside of school, always keeping to herself. Making her an easy target for bullying by one of the most popular girls in class, Shinohara Mirei, now known as Feirune in the other world. After spending some time reflecting after her reincarnation, Feirune expressed remorse for her past action and wanted to make an apology to her. Later in the series, she was informed by her reincarnated homeroom teacher she was dead, which greatly saddened Feirune and shocking reminder the reality of the new world they reincarnated in. Ooshima Kanata, presently known as Katia, once made a half-hearted confession to her. It was implied he was already uninterested in the opposite sex back then, he wanted to use the botched attempt to fit in better with the rest of the boys in class, intentionally choose Wakaba knowing he will get rejected based on her personality and history.

History
As the series progress, due to increasing prompt to reveal the numerous secrets that Filimøs was hiding from Shun's faction and unexplained disappearances from the academy, Filimøs revealed some of the status of the other Japanese classmates, including the current whereabouts of Wakaba Hirro from the request of Feirune, due to her guilt from her past life.

According to Filimøs, Wakaba Hiiro, didn't survived the ordeal in the new world.

Spoilers from Volume 5 of the Light Novel! Throughout the series, there was small hints that implied that Wakaba Hiiro was the identity of Kumoko. This was later confirmed in the Elf Village Arc, when a seemingly alive and unscathed Wakaba made an appearance. This greatly shocked Filimøs, Shun and his fellow reincarnations.

Spoilers from Volume 9 of the Light Novel! It was later reveal, Kumoko was not actually the real Wakaba Hiiro. But took on her appearance and form due to D's influence in the beginning of the story. Wakaba Hiiro was a false identity created by D, which she used masquerade as a high school student, partly to escape and slack off from her responsibilities as a god and enjoy Earth life.

Due to the mysterious explosion that kills off her classmates and teacher, D implant a piece of her memories into Kumoko, making her substitute to in order to hide her tracks and to trick the staffs of the underworld. This substitute soul which later became the basis of Kumoko, is made using a small sliver of D's real soul allowing her to take the appearance of Wakaba Hiiro. This greatly displeasure Kumoko, knowing her current existence was build on a lie.