Karen

Maybe because she had pretty much always gotten whatever she wanted or that it's simply in her nature, Karen never thinks it's impossible to accomplish a goal or do anything (even when it truly is at times). Her best qualities are her exceptional will, patience, and the pride in the bottom of her heart that refuses to let her give up easily. As such, the moment she left home, returning to her luxurious room under the control of her father stopped being an option, and the fire that had already ignited within her didn't get put out just like that when she instantly realized Shizuru was a partner way out of her league.
Karen might have been like a flower that grew up in a glasshouse, but her adaptability is surprisingly excellent. Despite all instructors believing she would be the first candidate to give up, she ultimately completed the entire boot camp, and even her peers, who initially thought she was a pampered princess, eventually had to hand it to her for her marvelous tenacity. She earned the recognition of everyone and went on to officially become part of Team Ratel, finally worthy enough to work alongside Shizuru.
As committed as she is, Karen, too, has suffered several setbacks in her journey moving forward, but she would immediately get back up and continue ahead. This quality is what makes her a dependable partner for her companions and an incredible, high-spirited member of the B.C.R.L. force. Sadly, judging from the present situation, her relationship with Shizuru isn't really making much progress, for Shizuru hasn't taken Karen's words seriously. It seems this is all unrequited on Karen's side, after all.

Although Karen is serving as a medic, she had pretty much never seen anything related to battlefields and casualties prior to her training, for even when she accidentally nicked herself on the stairs at home, several servants would immediately swarm forward to help her deal with the minor injury... As a result of that, the first time Karen received first-aid training in the B.C.R.L.'s training camp, her worldview was shaken.
The simulated wounds generated by first-aid instruments were exceptionally realistic, prompting many trainees who weren't used to seeing blood and gory scenes to faint or throw up before they could resume training. The instructor told them sternly, 'You have no business being a medic if you can't even handle this.' This led to quite a number of people giving up and switching to other military branches.
As might be expected, Karen puked her guts out and even nearly fainted from physical exhaustion. Despite learning the methods for bandaging and emergency treatment, she still had a hard time doing them right with her trembling hands. Yet, Karen—the first person who others assumed would be the first to throw in the towel—grew out of the pamperedness she had been showered in since young and forced herself to bear with the discomfort and fear to practice on repeat determinedly. Following an entire afternoon of repeated tries, she eventually completed the bandaging process required for the training. The instructor walked to her, confirmed her result, and reminded her to get some rest. Unexpectedly, she sat on the ground and burst into tears despite finally easing up. The instructor was left with no alternative but to ask Shizuru, who happened to be passing by, to take Karen back to the dorm to rest.
At present, having been through a ton, Karen is already capable of applying first aid on the battlefield efficiently, but she still remembers what it felt like to bandage someone's wounds with her own two hands back then. Her hands, which once couldn't grasp anything, are now able to save her companions' lives... She genuinely believes there isn't a job in the world better than this.

Before leaving home, Karen thought that love was equivalent to full-blown protection. Her father not only fully satisfied her materialistic needs but also never neglected her mental health, often showing her care and concern. Although he was constantly overly worried, fearing that she would be in danger—even a tiny little cut was too much in his eyes—she believed that this was the right kind of love.
That was until her father ignored her feelings and took it upon himself to arrange her matrimony. Shocked and furious, Karen suddenly realized that disregarding someone's feelings and imposing what one presumed to be good onto someone else wasn't the kind of love that could make one's loved ones live in bliss.
Running away from home, meeting Shizuru, joining the B.C.R.L.'s training camp, becoming Team Ratel's medic... In this process, Karen continually searched for an answer: What is the right kind of love? Despite being unhappy about her father's domination, she still can't help treating Shizuru the way her father did her. Pretty clothes, exquisite accessories—whatever it is she fancies, she will gift them all to Shizuru. However, Shizuru doesn't need those things and even feels troubled by them.
Karen went from watching Shizuru's back view to walking alongside the latter. Whenever Karen sees Shizuru smiling at the mention of her childhood friend, Karen will have a kind of sudden realization. The strange thing is, there isn't any indignance or sadness in her heart. The sight of Shizuru looking genuinely happy only fills Karen with a sort of relaxing, serene joy. She is happy, so long as Shizuru is.
Perhaps she has already found the answer to her question.