Offering some food for thought, can be quite lengthy :-)

I spent my afternoon sitting at a quiet, dimly lit corner to watch this movie, and by the end of it I was truly touched by the deep, profound story that this movie portrays.

Having received 11 nominations in the 56th Golden Horse Awards and winning 5 of them, with one being 'Best Film', I know I already have high expectations the moment I clicked into the movie, and boy did the movie not disappoint me. It totally threw me into a whirlwind of emotions. :")

Story and acting wise, I have almost nothing to pick on. The actors were brilliant in their portrayal and well, my ratings are clear enough, and you can watch and judge it for yourself.

Rather, I would like to bring up some themes that lingered in my mind after I've watched the movie.

[We've all been hurt before, and that's how we can become each other's sun.]

[A Sun, A Son]
The title of this movie holds two meanings, 'A Sun' and 'A Son'. What happens when a family is thrown into darkness when the 'sun' of the family is no longer there? What happens to the family when A-Ho has to move out of the darkness, what hope can he, or rather, they, cling onto?
This is a movie that speaks about relationships within a family: mother and son, father and son, elder and younger sibling, and many many more. But ultimately, this movie explores what it means to be a family, and to be yourself.
Also, note the use of the article 'a' for the title of the movie. Why is it 'a' and not 'the'? How does the difference in definiteness of these two articles change the meaning of this movie?

[Light, Darkness, or Both]
In this movie we have characters who stand out and thrive in the world brightly lit up by the sun. However, some recede into the darkness where they seek comfort and find out their own meaning and interpretation of what they're worth. But how about both? How does having both light and darkness in a character's life influence him in any way?

[Expectations and Hope]
For someone who has been in the light all along, how does he feel about it? How do societal and familial expectations weigh down on such a person? How does he find shade to rest and take a breather?
Whereas, for someone who was always in the darkness, will he be able to find his own ray of sunlight and move into a world where the sun shines brightly upon him and his future? Over here, how does societal and familial expectations differ from that in the aforementioned case?

[The Sun (literally)]
The weather changes throughout the movie helps portray the different settings and atmosphere for each character's feelings, emotions and state of mind. And I must say, the appearance of the sun (or the lack of it), as well as the amount of sunlight shining upon a character, plays a huge part in helping viewers understand what state of mind the characters are in. The visual significance of these scenes are enough in showing us the characters' emotions even without them having to portray them. That's how powerful and well-thought-out the cinematography is in this movie.

[Seize the day. Decide your path.]
This is a recurring slogan in the movie, and we can begin to wonder why it's mentioned in the first place (and many times after) and also how much it weighs on the different people receiving this piece of advice.

Well, that's all I can offer for some thinking after the movie ends. Do watch the movie, you'll not regret it ;)