Lapis' first known contractor who was forcibly contracted with her. While their meeting was not imaginably pleasant, Lapis' presence comforted Mikoto's loneliness and she responded in kind to "fulfill her desires". It can be assumed that Lapis' personality hadn't formed yet at this point in time as she only answered to her duty to fuse with her user. Lapis however realized what she had did to her master and began to show extreme remorse and fear for what she had done.
The hapless captain of the 35th Platoon who became her second contractor after Sougetsu made use of the Einherjar attack to have Takeru face it,inevitably fail, and contract with Lapis. Lapis begins her relationship with her new host in a very neutral partnership but insists on staying in her human form to physically cling to him and "act" as his little sister, an act that gained the ire of Takeru's classmates both in and out of his own platoon. Lapis remained mostly enigmatic towards him but showed extreme devotion to whatever Takeru's reasons for fighting was as to "fulfill her purpose" and Takeru's own desires. However, she showed immense amount of jealousy and mild irritation whenever Takeru praised another blade that wasn't her.
It was not until Takeru required greater power that Lapis revealed her true function as a godslaying weapon. Takeru however "rejected" her after releasing her abilities when trying to commit suicide with Kiseki and when the two along with Mari were whisked away to the Magic Academy, she avoided him. Takeru placed it upon himself to repair the strained relationship and approached Lapis to elevate their relationship from man and tool to that of a relationship between inseparable partners. Takeru's insistence on seeing her as another person and acknowledging her eventually takes root and has her share the memories of her guilt with what happened to Mikoto and how she fears she might do the same to him. Their trust is repaired but Lapis quickly undergoes a fit of jealousy whenever Takeru focused on the other girls and this fear grows to a point where Lapis fears that her willingness to monopolize Takeru for herself might lead her to take away Takeru's memories of the other girls and since she didn't want to make him unhappy, wished to undo the contract if it meant keeping him safe and content. Takeru's complete and utter trust in her once again repeals any doubts in their hearts and the two continued to rely on each other to fulfill Takeru's wish.
35th Platoon Edit
Overall, Lapis shows little to no concern in wanting to involve herself with the rest of the platoon. She never responds to them in any sort of way but refers to them in with honorifics when she refers to them when speaking with Takeru. The only person to successfully communicate with her was Ouka who approached her to work together in keeping Takeru safe from Lapis' own Godhunter process. Surprisingly, Lapis shows concern over them for the first time during the time Takeru and Lapis had to make a choice between saving the world as the cost of their existence and she mentioned their names in order to convince Takeru to back out of Mother Goose's offer.
Kyouya's Relic Eater whose naturally vitriolic and instigating nature clashed with Lapis multiple times as Takeru was forced to face Kyouya in combat a number of times. Even after Takeru and Kyouya made amends, Lapis was wary of Nero. Nero in particular seemed to be aware of Lapis' history as she taunts Lapis for staying in the form of her previous contractor, Mikoto when Lapis herself asks why she remained in Yoshimizu's appearance.
The female personality within the legendary blade Dáinsleif and Haunted's trusted blade and partner. Lapis' proud confidence in her blade quality and abilities naturally came to conflict with the similarly prideful Nacht. While Takeru's struggle against Haunted had Nacht continuously taunt the duo, Nacht was furious when Lapis and Takeru retaliated and forced Haunted to retreat.