1. it was long (not sure if multi-chapter, or looong oneshot)
2. angsty-drama genre
3. Rin is raped and murdered
4. Sesshoumaru kills her rapists (a bunch of bandits or something?) -- explicitly written
5. Sesshoumary was traveling with Inutachi so he couldn't protect Rin (and Jaken???), then they encounter a lady stuck under a roof (?) and she tells them the bandits went in this direction (where Rin and Jaken were).
6. I distinctly remember Rin being beheaded and her mouth in the shape of an O and Sesshoumaru thinking "were you crying out for your protector Rin?" or something like that...
that's all I have. :/