“Mari-chan and I go halfsies on everything.” —Author's Comment
Hanbunko (also referred to as 50/50 by the author) is Rishuu's 15th VOCALOID work.
The song focuses on Miku and her best friend, Mari-chan, who do everything together and share everything. Miku sings about how she loves everything Mari loves because they share half of everything. However, the song takes a dark turn when Miku mentions that lately Mari has been ignoring her in favor of a boy. Sad, Miku attempts to find out where the boy lives in order to get Mari-chan back. She decides that the only way to bring Mari back to her side is to cut the boy in half, so that they can both share again. However, after cutting the boy in half with a chainsaw, she finds that Mari is not delighted (as Miku wants her to be), but is instead horrified. The song ends with Miku singing "halfsies" to herself.