Do Ha (Kim) is a fearsome warrior who soars above the battlefield with his arched bow and lets loose an arrow that fells the Gaya general.

With the blood of his enemies barely dry on his armour, we next see him on the hangman’s scaffold, where he executes the general’s family and issues a warning to terrified onlookers that they will suffer a similar fate if they don’t fall in line.

But one person in the audience regards him with a steely glare. This is Han Ri-ta (Pyo), the vengeful daughter of the general who was hidden by her mother before soldiers snatched her away.

Ri-ta then appears before Do Ha with murder on her mind but, after a failed assassination attempt, an unexpected romance blossoms between them. Yet, duty bound, Ri-ta eventually gives in to her vendetta and strikes down Do Ha.

His spirit refuses to move on to the afterlife, instead latching itself on to Ri-ta and all future incarnations of her, as he awaits his own chance at revenge, all the way to the present day.

In 2023 Ri-ta is Kang Young-hwa (Pyo), a brave firefighter who has never failed to rescue someone from a fire, an impressive track record she credits to her deceased policeman father, who she believes to be her guardian angel.

We see her in action early on as she dashes into a flaming building, searching for a vagrant who is believed to be caught inside. She smashes down a door and escapes with the man and his pet dog.

The man safely removed to an ambulance, she begins to administer CPR on the dog, who her colleagues believe is beyond saving. But she manages to resuscitate the pup, both maintaining her perfect track record and making an indebted friend in the vagrant, whose appearance belies his secret identity.

Not quite so heroic is Han Jun-o (also Kim), a top star filming a public service commercial as a heroic firefighter. His character bravely saves a boy from a blaze but, once the cameras stop filming, he pushes off the child and makes him cry. This won’t be the last time his brazen actions upset someone.

Young-hwa’s televised act of bravery sees her cast in the commercial and she soon discovers how lousy a person Jun-o is when not putting on an act for the public. That doesn’t stop her from saving him when he faints in his van, which rolls into the Han River in Seoul.

Save is perhaps not quite the right word, since technically both die in the accident – Young-hwa in the water, Jun-o later in hospital. But both are saved by the spirit of Do Ha, who has never left Young-hwa’s side.

Do Ha’s act isn’t one of kindness. He saves Young-hwa for the express purpose of being able to kill her himself, and now he has the opportunity to do so thanks to his doppelgänger Jun-o.

After Jun-o is pronounced dead, his body is possessed by Do Ha’s spirit in the morgue and he goes straight to Young-hwa’s room.

She is shocked to see him alive, even more surprised to be hugged by Do Ha and a little confused by the knife in his hand. What she doesn’t realise is that he just tried to stab her. However, he failed on account of the mysterious force field that is protecting her from him.

Do Ha, as Jun-o, must engineer a way to keep Young-hwa by his side until he can figure out how to remove her shield and do away with her once and for all.

Boasting a watchable lead pair in Kim and Pyo and doubling down on its through-the-aeons romance and revenge, Moon in the Day is fitfully diverting and very familiar fluff. There are far worse ways to while away a weekday evening.

Let’s see what fate has in store for these star-crossed lovers.

Moon in the Day is streaming on Viu.