That is confused about the third couples ending, but I'm of two thoughts
1 they both died and went into the bell
Or
2 bc of what the shaman character said in the high-school timeline while playing the game, that the shaman turned into a half blood and the king went into the bell to continue helping him.
Choi Joohwan does not die during the ritual. He continues to live his human life in the modern world.King Lee Seon no longer exists as a wandering, vengeful ghost or demon. Because Joohwan relinquished his earthly ties and accepted him during the ritual, Lee Seon's spirit entered Joohwan’s body.Lee Seon now lives permanently inside Joohwan as his Momju-shin (몸주신)his personal guardian god. is a bittersweet "happy ending" because they didn't get to live as two normal, living boyfriends. Instead, they achieved an eternal spiritual marriage where the King finally belongs entirely to Chanseong, right there in the living world.
Update
Ja Chanseong said "your forgiveness lies with me". At this point, the king alr became a demon and Ja Chanseong had some unresolved resentment because the king had him killed by poison back then, so he chooses to accept the king and asks the king to accept him as he exorcises him as a shaman and have both their souls trapped in the shaman's tiger bells forever.
Trapping their souls in the tiger bells is not a total loss of peace, but a permanent binding of fate. The modern timeline and the guardian god element represent their reincarnation and spiritual resolution, allowing their deep bond to finally heal in a new life. Trapping the souls together means they are no longer tearing each other apart with hatred or consuming destructive desires. By choosing to be locked together, Ja Chanseong takes control of the fate that poisoned him, turning an eternal curse into an eternal holding of each other. It means that eternal entrapment was their version of peace, and it directly set up their happy ending in the modern world. If the king stayed a demon, he would be hunted and destroyed. If Ja Chanseong stayed resentful, his soul would corrupt. Locking themselves in the tiger bells was a sacrifice. They chose to freeze their conflict forever so they could stop hurting each other. For them, being trapped together in darkness was better than being separated or destroyed.
If the bells were broken decades later instead of centuries later, they would still reincarnate, but it would be a tragic, unstable reincarnation instead of a peaceful one. It takes hundreds of years for deep, murderous resentment and demonic corruption to completely wash away. They would still be magnetically pulled back to each other in the next life because their souls were fused together inside the bells. Instead of the king smoothly transitioning into a healthy, protective Guardian God, he would likely manifest as a highly unstable, overly possessive, or dark entity. He would protect Chanseong, but his energy would still be toxic and dangerous to be around. They would be reborn into a world and get to live and be together as lovers but they are still actively hunted by other shamans or spirits, forcing them to fight for survival all over again. The artist could have give them a little justice giving they never get to live together like the rest of the other two couples. I also had in mind because they tragic ending the king of the underworld will likely have heard about them and could have help them like he helped Dohui get to live spiritually locked into meeting his lover in lifetime after lifetime for eternity.
I think the story did well in showing us that the omega would eventually leave. I guess my problem was the omega deciding to leave AFTER finding out they were pregnant. The usual is leaving and then finding out you're pregnant, so to me personally it was a bit harder to sympathize with the omega...but whatever what do I know >.<











Story is cute and all, but I'm not strong enough for a love triangle ╥﹏╥