Developed by the Novus Orbis Librarium, Bell was to be used by Meifang Lapislazuli with the goal of becoming a Nox Nyctores. She was sealed in a Prime Field coffin and put aboard a train destined for the 13th Hierarchical City of Kagutsuchi.
On board of the train destined towards the Hierarchical City was Mai, Kajun Faycott, and Jubei. The three of them fought against NOL soldiers and the train eventually derailed into the nearby mountainside - Bell escaped from the coffin and stood atop it.  There she caught sight of Mai in the seithr-laced snow and walked away, but was followed by the young woman.  Bell warned her that something dangerous was nearby, also telling her that Kajun was fine and in no immediate danger. Mai reluctantly followed the young girl and named her "Bell" after the large bell that dangles from her collar. Soon enough, Bell fell from hunger and Mai fed her, beginning their friendship. The two girls huddled in a cave that night with Mai keeping her warm with her coat. The following morning, the two of them decided to look for Kajun and to complete Bell's objective - to throw herself into a cauldron; although she withheld this information from Mai. While searching the moutainside, they ran into Ragna the Bloodedge. 
Mai protected Bell from Ragna, who wished to destroy the Prime Field. She watched the two of them fight, being shocked when she realised that Ragna was using Soul Eater. The man had Mai by the throat, and Bell ran to him, punching his legs in a desperate attempt to make him let go. Thankfully, they were saved by Kajun, Taro Sasaga'e, and Shiori Kirihito.  Before the fight against the Grim Reaper could continue, they were interrupted by a vampire - the 16th Fuzzy. Bell immediately thought of it as the worst possible situation for him to have arrived, and multiple ghouls were summoned for the group to fight against.  Catching Mai in a daze over her fascination with the Azure Grimoire, she slapped her cheeks, telling her to get a grip. The group defeated the ghouls and turned their attention to Fuzzy and his Bone Dragon. 
After Fuzzy was wounded by Mai, Bell took notice of her spear, the Legacy Weapon - Gallia Sphyras: Outseal. She realised that there was no limiter on the spear and that it was incomplete. Ragna had Fuzzy distracted, but was nearly forced to activate the Azure Grimoire; Bell, Taro, Kajun, and Mai interrupted the activation, severely annoying Fuzzy, who had wished to see its power. Bell was knocked back by one of the vampire's attacks, and was caught by Ragna.  She looked at him, but he told her to not get the wrong impression, and that Fuzzy was currently a higher priority than she was. Soon enough, the fight ended as Meifang entered the fray and surrounded the group with the Wings of Justice. Thankfully for the group, they were teleported out of the area by Rachel Alucard and near the 11th Hierarchical City of Shinatsu. 
Near the area the group were teleported to was the Hazuki estate. Together, they travelled to it as it is Mai's family home. They were met by Julian, one of the maids, and were introduced to Rin Hazuki, who immediately jumped to the conclusion that Bell was her granddaughter and began to smother her in affection. She watched Mai fight against her father, Houichirou Hazuki and lose.  Bell later watched Mai train against Rin, who used Vision throughout the fight. Later that same day, Bell was washed by the Hazuki matriarch, who told her that she believed that Mai could probably defeat Houichirou. The rematch, however, was interrupted by Kokonoe and Litchi Faye-Ling.  Mai took Kokonoe's offer of joining her to the nearby cauldron, and Bell, Shiori, Taro, and Kajun joined in her decision.
En route to the cauldron of Shinatsu, Litchi explained to Bell and Mai that they were needed by Meifang to smelt something as she had opened up various facilities that had been closed after the Ikaruga Civil War. Before Bell could explain her goal to Kokonoe, she was snatched into the air by a Fuzzy, startling the group as they had not realised that there were multiples of them, not just one. Bell was taken through a portal that led to the cauldron itself, and Mai followed after her. When they awoke, they were surrounded by Fuzzies and Meifang herself.  As the battle progressed, Meifang explained her goal to the girls, and Bell elaborated to Mai that the civil war begun because certain people wanted to harness the power of the Black Beast. Thankfully, the girls were saved by the arrival of Jin Kisaragi. 
With Jin battling Meifang and Mai dealing with the Fuzzies, Bell ran towards the cauldron, determined to stop Meifang's plan of creating a Nox Nyctores by throwing herself into the Boundary. She told Mai of her plan, but her friend refused to agree to the idea. Regardless, Bell ran towards the cauldron and an intervention occurred - she was met by Trinity Glassfille and the two came to an agreement. Trinity would take over Bell's body and place her spirit into Outseal to act as its limiter. Now inside Outseal, Bell allowed Mai to truly use her weapon and encouraged her to fight. 
Meifang was eventually killed by Mai. Bell still resides inside Outseal, and is by Mai's side forever. Eventually, her body would be inhabited by Platinum the Trinity.
- BlazBlue: Variable Heart, Chapter 04
- BlazBlue: Variable Heart, CHapter 05
- BlazBlue: Variable Heart, Chapter 06
- BlazBlue: Variable Heart, Chapter 07
- BlazBlue: Variable Heart, Chapter 08
- BlazBlue: Variable Heart, Chapter 09
- BlazBlue: Variable Heart, Chapter 10
- BlazBlue: Variable Heart, Chapter 11
- BlazBlue: Variable Heart, Chapter 12
- BlazBlue: Variable Heart, Chapter 13
- BlazBlue: Variable Heart, Chapter 15
- BlazBlue: Variable Heart, Chapter 16
- BlazBlue: Variable Heart, Chapter 17