#kohasen

She's fierce, formidable, and confident. She faces off against both Tsukasa and Moz despite knowing they're stronger because it's something she believes she needs to do.

Loyal. Kohaku is the first person to trust Senku in the stone world, and her trust in him never wavers. She continues to support him until the end (even when she thought his decision to free Whyman was strange and he said "please," she followed through). This applies to all her friends and Ruri, whom she would do anything within her power to help and keep safe.

(I do think you see her loyalty to Senku the most--he is the protagonist, after all. She has never been his enemy and follows through with his decisions despite not understanding all the science behind it.)

Strong and resilient. Kohaku is strong physically, mentally, and emotionally. Physically, she's the most versatile warrior; she has strength, agility, eye sight, and nimbleness. It allows her to come in clutch on several occasions. Mentally, she's disciplined with training, as well as with how she carried the hot springs water to Ruri daily. This also ties in with emotionally in how she accepts her father's scorn and becomes the "troublemaker" of the village just to improve Ruri's chances of surviving (more on this later since I think it mirrors Byakuya). She is never the victim of her situation; she makes a choice and sticks by it. She does what needs to be done.

Empathetic and emotionally intelligent. Between understanding Chrome's feelings towards Ruri and Senku's feelings towards his dad, she has shown a lot of awareness to how people really feel.

Self-reliant and selfless to a fault. She doesn't asked to be saved and will risk herself to save others without a thought. It's the reason Senku or Gen have to stop her (or fail to) when she runs off to save someone against better judgment (Chome when kidnapped, Treasure Island arc when everyone was petrified, Suika on multiple occasions). She intends to help others regardless if anyone intends to help her.

Open-minded and firm on her beliefs. This was also shown earlier with how she stands her ground to sustain Ruri's motivation/will to live. In addition, though she doesn't understand the intricacies of science, she's still able to believe in it and defend it. She's also not willing to risk sacrificing anyone, which we see when she goes to look for Suika during the grand bout.

Alright, back to how Kohaku is similar to Byakuya. Byakuya is acclaimed to be best anime dad (and he absolutely is; no shade there) for spending decades collecting platinum for Senku.

(Chapter 115)

See that face Senku makes there? You know where he also makes a similar face? Chapter 17.

As in, Kohaku makes a similar sacrifice with the hot springs water and becoming the "troublemaker." Kohaku is very willing to sacrifice herself for someone she loves (not needlessly; she keeps her wits on her). She may look like Lillian, but she has Byakuya's heart. (And yes, what she does is not to the same extent or scale as Byakuya, but she is/was a child and does not have the same kind of knowledge. I do think she has the same almost unfounding belief in Senku and saving Ruri.)

Piggybacking off of what she chose to become, here's a Q&A that states Kohaku can be both solitary or social.

Which means she has more depth than what is usually portrayed in the manga/anime likely secondary to it being a shonen series with an outstanding male cast (yes, I've said this twice because wow, what a cast), but also because we only really see her post-meeting Senku. Kohaku brought him to the village and gave him the manpower he needed, but he, in return, gave her companionship (and yeah, a cure for Ruri). It's easy to forget that she was mostly alone prior to this.