Title: 一笑傾城(One Smile Turns the World Upside Down)
Drama:微微一笑很傾城 (Just one Smile is Very Alluring/Love O2O)
Singer/Song: 汪蘇瀧 (Wang Su Long/Silence Wong)
Lyrics: 林昌磊 (Finale)
Song style: Medium tempo, bubble gum, ballad
Theme: Falling for somone

Silence Wong Version (Just One Smile is Very Alluring/Love O2O OST)

Special Actor Version (performed by supporting Actors of the drama listed as follows):
張赫 (Ryan Zhang) as 甄少祥 [真水無香] Zheng XiaoShang [Zhen Shui Wu Xiang/Scentless True Water]
白宇 (White Bai) as 曹光 [微光] Cao Guang [Wei Guang/Dim Light]
鄭業成 (Zheng Ye Cheng) as 眉 [莫扎他] Hao Mei [Mo Zha Ta/Mozarta]
崔航 (Kyle Cui) as 丘永侯 [猴子酒] Qiu Yong Hou [Hou Zi Jiu/Monkey Wine]
張彬彬 (Vin Zhang) as KO

Previously, I noted Annual Ring from the Journey of Flower is written by Silence Wong, he also wrote a lot of songs for this 2016 Chinese drama.  This one is the opening theme. I know many people translate Yi Xiao Qing Cheng as alluring. It's not wrong but that's not what the words literally mean. Qīngchéng literally means taking down a city (and even downfall of an empire). See this wiki entry for the history on this word So in this context, it's not as simple as saying that a smile is just alluring/beautiful but that it's so beautiful it flips your world upside down, love at first sight kind of feeling. Hence I went with this expression.

LYRICS

INTERPRETATION

Summary

This is a song about a guy falling for a girl at first sight for her beauty and grace during around June/early summer, and not confessing it directly but indirectly.

Detailed 

Disclaimer: this is my interpretation. This time, I did not translate as literally as I thought I would have because there were too many of these advanced phrases that translating them literally makes little sense. In fact, I'm taking my own little Chinese lesson since some of these words are foreign to me too.

First two lines describe the guy as being very indirect. He wants to confess but it's done indirectly. The first line uses 輕描淡寫, which literally is softly sketch lightly write, which means not being very thorough and understating key points. In other words, he tells his wishes but not directly, hence I used vaguely. The second line says he gives her glances, but packed in those intense stares, he actually has many many things to say (千言萬語) such that he can talk on forever and it won't end(說不盡).

The next two lines are fillers, saying other people are busy with material things (treasure) and miss out on interpersonal and natural things (maybe hinting at feelings?)

The next part is the chorus which will be repeated so I won't repeat this later twice. The next two lines are filler to set up imagery, probably describing even when there's so many people and cars surrounding him, with so many people busy with their own lives, yet he only focuses on her smile, which is like a shining light on him. You know that cliche scene when the worlds stops, and there is only him and her; that's what these lines are about.

The next four lines states that he finally understands what love is and describes what his love feels like, like a bike ride under the shades of tree in a summer breeze.

The next three lines is saying he acknowledged that he fell in love at first sight with her smile. He wouldn't dare say that it's love yet since the most that they have done is watch sunset next to each other...no hand holding?

The next five lines is describing his wishes. That's where his heart is going towards, to take her sight seeing everywhere and to spend the rest of their lives together (using writing a book as a metaphor) through laughter and tears and thick and thin. And that concludes the end of the chorus that repeats

The next two lines of the next verse describe more about him meeting her. He met her unexpectedly but the meeting was unforgettable and lingers like perfume. He was entranced by her grace and beauty. I didn't give the literal translation of 驚鴻 which is startled swan, since I don't have any way of linking that to grace other than swan. Other dictionaries I searched said wild goose...so I just stuck with the idiomatic translation which is a beautiful and graceful woman.

The next three lines is just filler saying now is a prime time in his life since he's met her so he shouldn't disappoint and take this opportunity to confess (in my opinion that is). And since earlier it was mentioned this was during summer time, so June scenery is described that wind fills all streets and alleys and caress the blooming flowers on the paths. Perhaps the blooming of flowers implies his blossoming love. It sounds like the chorus is the confession.

So my conclusion is, this song is about a guy who falls in love at first sight for a beautiful and graceful girl that he met by chance. And he's been dropping hints and is pursuing her with intentions of spending the rest of his life with her forever through thick and thin and laughter and tears. And the song implies he either intends to confess or has confessed (which is why June flowers are blossoming and spreading throughout his world perhaps).