halyosy, also known as his real name Halyosy Moly (森晴義 Mori Haruyoshi), is a producer and a former member of the defunct professional music group "absorb" (halyosy, that, and is). He's mostly known in the Nico Nico community as an utaite.
He has created a number of songs mainly using the Crypton Vocaloids.
His hit, "Sakura no Ame" was a reoccurring song in the Weekly VOCALOID Rankings after its release in February 2008, lost its popularity for a while, and then received another surge in popularity when absorb performed the song live at a high school graduation in March 2009, causing it to take the #1 spot and become a popular graduation song for high schools across Japan. Many of his works have also entered the Hall of Fame.