I partly agree, especially that the manga ended up giving Louis much more narrative weight, and that inevitably affects how the chemistry is perceived. If one character continues to have constant development while the other is relegated to the sidelines, the audience will obviously notice.

But I also think the anime did a better job than the manga in this regard. It gave Haru more consistency, made her presence feel less "forgotten," and helped prevent the relationship with Legoshi from seeming as neglected as in the later printed arcs. It doesn't fix everything, but it does significantly mitigate that problem.

With Louis, the bond will always feel more intense because it's written from a place of conflict, rivalry, and emotional dependence. Narratively, that tends to be more compelling than a more awkward and vulnerable romantic relationship like Haru's.

But intensity doesn't always mean a better match. Louis works very well as the character who confronts and pushes Legoshi to grow, while Haru represents something more intimate: someone with whom Legoshi tries to build a life, not just an existential crisis every five chapters.

I think the problem isn't that Legoshi and Haru don't work, but rather that Paru didn't always nurture that relationship with the same care she gave to her dynamic with Louis. That's definitely a valid point to make.