While it may not be necessary to watch 1 before 2, it might make more sense since 2 is the prequel to 1. However, I watched 2 before the first series and for me, it was not necessarily the smoothest of transitions. But the story is simple, basic, yet conveys a sense of life as it really exists. One comes to terms with who he is and the other does not. There are only two characters in these series and so the whole story is shouldered on the strength and conviction of these two young men. Mon and Oak are the powerhouse couple in BL today but are not recognized as so. Just brilliant acting.
See my full review at BLBliss.com.