Yes, it's a BL, but really the story is about healing onself after being hurt, growing up, and putting yourself first. I guess some things you can only understand when you have experienced enough things, but it's a really nice movie.
You have to guess some things, but it's all given the through the subtext. You understand why Ba Da is there, and also Tommy's choice. Sometimes we have to put ourselves first, even if in doing so we hurt other people.
I also enjoyed the Ba Da maturing and not depending on others, also being able to say no when it was needed despite being hard. He found himself.
You might say it was not necessary for Tommy to leave for a while, but some things can only be pursued alone because it's our own personal journey.