I'm not sure if you consider it as a bug but
during Quang Phong's epilogue he first comes out with the purple pop star clothes (with his old face on) then when he's about to confess his identity there are suddenly two sprites of him.
As for the routes...I got The Anh's first so I'll start with his.
The Anh
The background music during The Anh's route is creepy. When there was a scream my heart actually jumped with fright! LOL very effective. And I know that you haven't put the epilogue for his route yet so I'm kind of disappointed in his route since it suddenly stopped at a weird ending. I want to know what's going on with him! Why did he kill those kids? What will the MC do when she finds out? Will she find out? And how will The Anh react if she knew or not knew? Will she even see him again? I wanna knowwww!! XD XD
Khoi Vi
It was a very nice route and I was sad when he died right in your arms. It did surprise me when everything was explained in the epilogue. Before that I thought you were going to leave it just like that. It's not the way I would have done it. LOL But even if the style is different it was still good.
Quang Phong
I don't understand why you think he's not attractive. There are some times when I think he looks like Kurogane from Tsubasa Chronicles. (who is really really hot! XD XD) I agree with many of the others. Quang Phong doesn't look that bad. In fact, I found him attractive. He looks like the type of guy I'd fall for (in terms of drawn characters anyway).
Having him reveal himself as the pop star was kind of...disappointing. It would have been better if the message left behind that route was beauty on the outside didn't matter as long as they loved each other. And I laughed when he pulled off his mask to reveal his real face. Plus, OMG THE BUNNY EARMUFFS!!!! SO CUTE!! HAHAHAHAAHA
Vu Minh
No epilogue. But I like his route. I wonder what you have planned for his after story...
The CG's would have been prettier if they were colored.

And you really did pull it off. Even though it was short a lot of things happened and I really enjoyed the game. I can't say who's my favorite because they're all equal in my eyes. ^^ You're really good. And the story adds to the fun in the game. I loved it!