This was a pretty enjoyable drama to watch overall, although it is very flawed and therefore I really can't give it a very high rating. I adore both main characters, but the production quality is poor and the writing is often sloppy. The acting varies; sometimes it's quite good, sometimes it theatrical to the point of being slightly ridiculous. Since the actors do prove their skill in some scenes, I'm guessing that in other scenes it is the direction they were given that I didn't care for.

I'd probably only recommend this because of the two main characters – Zhao Yun Lan and Shen Wei – and their relationship... which is kind of ironic, since it is overtly romantic in the source material, but comparatively subtle in this drama. It looks identical to queerbaiting in western television, but in this case it seems that they probably tried to retain as much of the essence of the relationship as they could given the restrictions placed upon it by Chinese censorship.

Perhaps it is because they are so different that they are so drawn to each other. Shen Wei is a distinguished but modest, mild-mannered professor. Zhao Yun Lan is unrefined, messy, and brazen. In the process of working on cases together, they seem to naturally counterbalance one another and quickly become an integral part of each other's lives. They're referred to as friends and they're characterized as a "bromance" in the synopsis, but that is misleading in my opinion. Yun Lan shows zero romantic interest in any other character, and it's indicated that he doesn't really have an interest in relationships generally; he's been single his entire life. He doesn't flirt with other characters – but he is frequently flirtatious with Shen Wei. He is quick to deny having feelings for another character, but when insinuating comments are made about his relationship with or feelings for Shen Wei, he never denies it. Moreover, despite only knowing Shen Wei a few months, there is a clear distinction between how he regards him and how he regards his other close allies he's known for years. It is even more quickly apparent that Zhao Yun Lan is the most important person to Shen Wei. There is an intensity to their dynamic that just doesn't seem platonic to me. It's a censored romance, not a bromance. (Nothing against close platonic friendships, I just don't see this as one.)

There's a secondary "bromance" in another odd couple, Chu Shu Zhi and Guo Chang Cheng. The dynamic between most of the Special Investigation Department co-workers are quite sibling-like in that they enjoy teasing each other and there's clearly some affection there, but they don't seem especially close. Therefore, the time spent on developing the intimate relationship between these two characters makes them stand out. Chang Cheng reminds Shu Zhi of the brother he lost and that surely accounts for a lot of his affection towards him; he wants someone to fill the void that his brother's death left him. But by the end of the story, it doesn't seem to me that Chang Cheng is just a placeholder for his deceased brother. Rather, Shu Zhi comes to genuinely admire him for his own strengths – and Chang Cheng, for his part, is unwavering in his adoration of Shu Zhi, even when Shu Zhi tries to scare him off for his own safety. The lines of this relationship are more blurred to me than the one between Zhao Yun Lan and Shen Wei. The intimacy and implied commitment seems decidedly less brotherly and more romantic, but there is still an element of brotherhood there. I guess it doesn't matter much whether it is one or the other or both; they're a cute duo regardless.

The other characters who work at the Special Investigation Department are enjoyable enough, but a little more forgettable for me. (Especially Wang Zheng and Sang Zan, who seem the most under utilized.) Zhu Hong is probably my favorite of them overall, although watching her struggle with her one-sided crush on a co-worker was a bit painful to watch. Da Qing and Lin Jing both sort of have romances with minor characters, but they matter so little that I wasn't able to feel particularly invested in them. The minor characters who fall into the "monster of the week" category were also pretty forgettable overall. Many of them make reappearances, but I found myself struggling to recall which one was which – a problem I don't typically have even with large casts of characters.

As far as acting goes, Zhu Yi Long stands out the most to me given that his roles are the most diverse. In addition to portraying the various sides of Shen Wei – the awkward professor, the Batman-esque masked hero, and the naïf he was 10,000 years before the present – he also portrays his villainous twin brother with dramatic flair. He is really able to showcase his versatility in this drama. Bai Yu also does an excellent job at conveying the multifaceted nature of Zhao Yun Lan. Aside from the two main actors, Jiang Ming Yang has some standout moments as Chu Shu Zhi. Although the character is generally very gruff, the actor really went all out during a humorous "personality changing" episode, and his more serious moments were some of the most emotional parts of the drama for me.

The OST is quite lovely overall. The opening theme is catchy and I'm afraid I'm going to have it stuck in my head for a while. I don't typically bother watching the opening or ending credits of dramas, but I often watched the opening of this one. The soundtrack really drives home the bittersweet sentimentality of the story.

Which brings me to the weakest part of the drama. The premise of the story is reasonably good, but it is not executed well. The plot is messy and the pacing is uneven. Even taking into account that I'm mostly reliant on English subtitles, the dialogue is very awkward at times (mainly between secondary/minor characters). Fortunately, the main relationships and characters are able to carry the show (at least, for me); had it not been for that, I would have dropped it because calling the rest of it mediocre would probably be generous. The CGI isn't particularly good, but I honestly don't expect a whole lot from Chinese dramas in that regard, so that doesn't really factor into my evaluation of it. Probably the most perplexing flaw is that there were many occasions where the audio switched between the actual voice of various supporting characters and the voiceover. It's a relatively minor detail, but it makes the drama seem unprofessional.

In spite of its flaws, I do consider Guardian worth watching because I think many viewers are like me - if you make me fall in love with your characters and their relationships, I'll be wiling to overlook a lot. Indeed, I did become quite attached, so I will definitely be giving the novel a shot.

tl;dr:

- the two main characters are multifaceted and portrayed well
- the main relationship is the highlight of the show, despite being played down due to censorship
- some of the supporting characters are good, many are forgettable
- the plot isn't particularly great, the dialogue is sometimes awkward
- production quality is poor