That depend of the song/PV you saw. You know, vocaloids (at least the official ones) doesn't have an specific personality or relationship. I will give you one of the songs that Gumi and Len sings: ah wonderful nyan life(I think that's the name).
That shows Gumi and Len. You can look it up on youtube. Anyway, some songs don't show Gumi and Len.So I gave you the answer.
Hope you understand. :).
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.