The longest promise tells the story of the main lead's promises to each other. What both of their promises are, you will find out when you watch the drama. The male lead fakes his death to escape injustice and spends his years cultivating in a mountain as a Priest. Years later, the woman (female lead) who is prophesied to kill him becomes his disciple.

First of all, the drama has the most stunning fairytale-like visuals, with beautiful scenery, fight scenes and CGI I've ever watched. The story's logic always makes sense, has great pacing, not too slow or too fast, there are no stupidly, annoying characters, no fillers. Most of the screen time is given to the male lead, female lead and second male lead. I honestly did not find it boring even for a moment.

The male lead is one of the most powerful cultivators, he becomes a Priest to hide his identity as the Crown Prince that was wrongly accused. He is mature, aloof and wise. Female lead starts off as being quite immature, reckless and foolish. But she is also street smart and very brave. The main leads have many cute and funny moments together however this is a slow burn romance. As the male lead is a Priest and also her Master, their romance is forbidden so don't expect to see them in a proper relationship. Their love is very subtle and unspoken, they care and protect each other no matter what. Male lead spends a lot of time teaching her not only powerful magic techniques but how to be more mature and responsible. I found their romance very refreshing as it was built on trust and care rather than insta-love.

A big part of the drama is the second male lead who has his own story that connects with the main leads. I very much emphasised his character and loved all of his scenes. He is not your typical second male lead that's obsessed with the female lead. He cares for her but also wants her to be happy with whoever she ends up with. Despite his tragic love story, he still has much love for his people and I admired everything he did in the drama.

The only thing I did not like about the drama was the final villain that appeared in the last two episodes as it kind of came out of nowhere. There wasn't enough build up to find out who he was, where he came from and how much of a threat he was. But regardless of that, I very much enjoyed how it all played out even if it was heartbreaking to see it.

If you've read this far, don't waste time anymore and just watch this wonderful drama.