はんぶんこ。 (Hanbunko.)

www.youtube.com/watch?v=JZMEl49qmeE

50/50 is a song sung by Miku.

Trivia

 * The Vocaloid Mari-chan makes her first appearance in this song.
 * This song is also called "Halfsies" or "Halvsies".
 * This song might appear in a Project Diva game, but the game will be rated M for Mature if it does.
 * This song gets a novel adaption as chapter 3 in the upcoming book "Vocaloid: Hatsune Miku and Friends".
 * Miku and Mari-chan are both sixteen, but they like to play in the sandbox (usually enjoyed by 3 to 6 year olds).