Any ideea who the other characters are?

Miku with a veil and Kaito the angel of death (lol)

Here:
http://www.nicovideo.jp/watch/sm10282629
( Song by HitoshizukuP . In fact, by the same team who did Synchronicity )

for those who've seen the video:
Kaito: "omg you turned my loli into a shota!"*shoots*

SO... RIN LOVES MIKU,BUT SHE WAS REJECTED, THEN, SHE TURNS INTO LEN AND THEN MIKU LOVES HER ( AS LEN) BUT KAITO LOVES RIN SO KILL MIKU AND LEN/RIN GAVE HER LIFE TO MIKU SO SHE DIE

THAT ALL WHAT I GET

kaechan19 said:
SO... RIN LOVES MIKU,BUT SHE WAS REJECTED, THEN, SHE TURNS INTO LEN AND THEN MIKU LOVES HER ( AS LEN) BUT KAITO LOVES RIN SO KILL MIKU AND LEN/RIN GAVE HER LIFE TO MIKU SO SHE DIE

THAT ALL WHAT I GET

that's pretty much right, except that they (rin, mostly, but miku too) both are cursed and punished at the end.

but if rin turned into a boy, should we remove the tag "len"

gacon_lonton said:
but if rin turned into a boy, should we remove the tag "len"

Not at all. Len is Rin's mirror reflection and in some senses they are the same the person. Len tag stays.

I never wanted to beat Kaito that bad until I heard this song.