hot take: chihiro and iori getting together would be an objectively bad handling of their characters
ok like first of all. enjoy what you will i do not believe in policing what people like. BUT! from a narrative standpoint, i don't think a romantic relationship would be satisfying for either character.
the way iori and chihiro interact reads as profoundly unromantic. now, i would love for them to become good friends in further arcs, especially in the context of some of the parallels below, but what currently defines their relationship is a sense of loss. specifically, they're both each other's what-ifs, though its more an "i want to be you" than an "i want to be with you". up until the masumi come in, iori is living a fairly normal life- she goes to school (insert obligatory 4+2=12 reference here), has friends, and is just an average, well-adjusted person. this is what chihiro's life could have been, and its a sense of normalcy that he never got to have being occupied with his revenge quest. in the same way (and this is addressed pretty explicitly in the manga itself), iori sees chihiro as someone with something she doesn't: memories of his father. even if his life is objectively more dangerous and likely less happy, he gets to live knowing the truth, not living in a sorcery-induced lie like she is.
i think the broader theme here is the idea of "agency" and "memory". at the end of the arc, iori chooses to remember her father, which narratively solidifies chihiro's choice of "memory" as preferable to her life of "ignorance". it also puts agency in her hands, something which she has been deprived of; the gratuitous aura framing of chihiro + the masumi in this arc kind of sets this up too, with her getting her big power up after she remembers/seizes agency. its kind of important here to note that these parallels only arise after the loss of both their fathers (chihiro living happily in the mountains and iori wanting to live with her father despite the ostracization). but anyway, i don't think this setup lends itself particularly well to romance. iori needs to grow into her agency (which is currently based on reconnecting with her father), and that choice would narratively serve as a continuation of theme of loss with chihiro. in a sea of dead fathers, she has the chance to make new memories with hers- why shouldn't that be her focus?
beyond their introductions, i think a romantic relationship would kind of distract from their respective character arcs. kagurabachi as a series puts a lot of emphasis on fathers: chihiro and kunishige, the sazanamis and kyora, iori and samura, so on and so forth. it's clear that iori's arc centers around her relationship with samura considering that he's mia right now, that conclusion is probably going to have to wait a while. a romantic relationship with chihiro would distract from this narrative focus. i think there's some inherent tension with how samura favors chihiro, though not necessarily because he likes him more than his own daughter. no, he's just a coward. he can't face her because it means acknowledging that he took the easy path out, and more importantly, that he defied her wishes. it would be a little awkward for iori and chihiro to get together considering this. more than likely it would counterintuitively regress both relationships as samura continues deadbeat dodging in favor of his in-law, which has no narrative purpose because these things have already been established.
as for chihiro, i think it's a little more complicated. a lot of his character is predicated on the interrogative who? who does he fight for, and why? while it remains to be seen, i do hope that his arc deals with his inherent capacity to care vs his desire for revenge when addressing this. but anyway, the easiest answer to this question is kunishige. its already been established that this is an unhealthy lifestyle for chihiro; the best continuation for him is to discover a new reason to fight, or at least one that isn't just "kill the guys who killed dad". positioning iori as a romantic relationship of utmost importance doesn't do this particularly well. it just replaces one person with another (i imagine a "canon" explanation to be something along the lines of the enchanted blades causing suffering for her), which is not productive for chihiro's character growth. what he needs is a broader moral compass.
this last reason is more a meta-constraint than anything else. despite her presence in the past arc, we still have much to learn about iori. while her status may change, as of yet she is mostly a side character (which i believe she will remain). being a side character, there isn't as much time to develop multiple narrative focuses around her. any meaningful relationship with chihiro that addresses these previous notes would distract from her relationship with her father and vice versa. i would hate for a character with so much potential to become nothing but the "love interest". she's lowkey my goat.
but for the question we have all been waiting for. if chihiro were to be romantically involved with someone, who would be the best option for him narratively? apologies to any hakuhiro anti-truthers, but i think it would be hakuri. apart from the fact you could take their first meeting, put some sparkles on it, and get a half-decent shoujo premise, hakuri presents a much better option in terms of growth for both characters. for hakuri, it's the premise of care. he comes from a background where any love he is given is violence. some may argue that chihiro's love is similarly violent, just not explicitly abusive, but i think this misses the mark. not only is chihiro's mission based on protecting kunishige's legacy (removing the blades so his father is not complicit in the deaths they cause), but it is his grief that is violent, not his love. hokazono goes to great lengths to communicate that chihiro is an inherently gentle and caring person, just one who hides it beneath his thirst for revenge. as for chihiro, hakuri is something that iori is not: he is achievable. not in the "iori is out of chihiro's league" sense, but in what they both represent. specifically, no matter what iori chooses, she will always represent something chihiro can never have. she is an impossibility of sorts, first as the normal, well-adjusted life unavailable to him and then as the chance to reconnect with her father. it shades any relationship between the two of them with a decidedly melancholic tone and is an uncrossable distance between them. but with hakuri, chihiro can achieve something, and is in fact already working towards it in canon. he can become his samurai. in popular culture, samurai are typically associated with concepts like honor and righteousness (bushido), which fits perfectly with chihiro's broader character arc of finding a new reason to fight. his relationship with hakuri motivates him to be better, something actionable instead of impossible. while it can be argued this doesn't need to be romantic, what isn't debatable is hakuri being centrally important to chihiro, more so than any other character in the series. iori has already been abandoned enough; she doesn't need samura asking why hakuri smells like chihiro and she doesn't.
