Blood.
Soaking the once pristine white carpet, it also dotted the walls while it's metallic tang lingered in the air.
Len stared in horror and revulsion. Blood-spattered and smiling sweetly, his mirror-like twin sighed as red liquid dripped from the weapon between her small fingers.
"What? You don't like your gift?" she pouted, "I thought it would make us closer now that she's gone."
Len couldn't answer as a sob well up in his throat. He knelt down and tentatively hovered his fingers over the gashes in her chest. His fingers trembled before her investing heart and he withdrew them.
"Why?" he managed to choke out.
"Because," she sauntered over to Len, hugging him at his side. The knife grazed his side, the blood smearing onto his shirt. Rin rested her head on his shoulder. A light giggle passed through her lips making Len shiver.
"I love you."
This is what happens when you listen to too many creepy Vocaloid songs, marathon Mirai Nikki, scroll the Kagamine Len tag on tumblr, read Edgar Allan Poe in English class, and decide to update late for Halloween. Besides, there needs to be more Yandere!Rin out there. Len's not the only mentally unstable Vocaloid!
That aside, I would like to thank my Beta LonelyButLovely for her assistance in helping me write this!