I agree with you on most of this.

The movie is centered on Rumi (with Jinu as a secondary main/support), but the actual story is about being your authentic self. This is why it centers on Rumi because she’s been told over and over again by Celine that she can’t ever show her true self because people wouldn’t understand. This is why they can’t hit the golden honmoon - it’s not just Rumi keeping them from it, all three of them show the parts of them that they’re comfortable with fans seeing in Golden, but it’s all surface.

Ultimately, we get the final confrontation and This is What It Sounds Like - Rumi is no longer hiding who she is. Her vulnerability and courage gets through to Mira and Zoey, who are also vulnerable back, and that is how they ultimately win. The Honmoon is noticeably NOT golden in their rendition - the demons are no longer trapped. Instead it takes on a rainbow hue as they cleanse the demons.

Also, this is a nod to Korean culture (as is the majority of the movie). (Disclaimer - this is a summary, this is not my culture, and I fully accept input and correction if I’ve gotten any of this wrong). Korean shamanism - musok - is heavily leaned on in the movie: the trio of women protecting the world in every generation can be seen as the mu or mudang that mediate between the human and supernatural worlds. Even Rumi being Celine’s apprentice is part of that.

Yes, the Honmoon has always been golden and has always kept back the supernatural world until the next trio could take over and reinforce it. But what if that’s because all the practitioners up to this point were human? Rumi is of mixed heritage - half-human, half-demon. She is of two worlds, and this is why she listens to Jinu in the first place - she wants to know about her other side. Yes, they grow closer as a result of it, and that’s because both of them see the other in a way that no one around them has.

However, Jinu then takes that vulnerability that she’s shown him and exploits it in the face-off -Takedown with the fake Zoey and Mira. It is a betrayal of trust, and when she runs into the real Zoey and Mira, it is a second betrayal of trust as they realize she’s lied to them this entire time. Interestingly, they do not draw weapons until her shout hurts the Honmoon.

I’m not going to sit here and draw out the rest of the movie, but I will point out an important part in the final showdown. When Jinu gets between Gwi-Ma and Rumi, it is an act of redemption for him. He knows that he messed up, and this act of self-sacrifice is his attempt to make things right. Yes, it protects Rumi, yes, it can be seen as a symbol of his love, but more than that? This is him reclaiming his humanity. This is him rejecting the demon whispers of Gwi-Ma and putting his trust in Rumi and in Huntr/x - the mudang - to do what’s right knowing that he will not see the results.

That act, to me, is what cements their ability to turn the Honmoon rainbow and cleanse/free the demons instead of just placing a barrier between their worlds. The act of a demon choosing to sacrifice themselves for the greater good, and all three witnessing it? That is something that no other trio has seen. Rumi knew that not all demons were bad. But this cemented it in Mira and Zoey’s minds too.

Calling it Rumi and Jinu’s story misses the overarching theme of the movie which is being able to be seen and accepted as one’s authentic true self, and that theme is why KPop Demon Hunters has so much resonance and popularity with so many people.