ココロ (Kokoro)

KOKORO (ココロ/Heart) is one of the more notable songs sung by Rin Kagamine and produced by Toraboruta-P. The song is very popular among Vocaloid enthusiasts and has spawned a large number of covers and PVs.
 * Nicovideo Broadcast
 * Youtube Broadcast
 * 「ミクの日感謝祭 39's Giving Day Project DIVA presents 初音ミク・ソロコンサート～こんばんは、初音ミクです. ～」's ココロ

Background
The song talks about a robot made by a lonely scientist, but she is missing something that can't be found in a program: A Heart. Many years after her creation, her creator passes away, leaving her alone for several hundred years. Eventually she begins to wonder about the man who created her, and accesses his research. Discovering more and more about the reason the scientist created her and her Kokoro, the robot is moved and is awakened to a world of new feelings. However, the Kokoro which she found herself was too great for her fake body, and after some time the robot passes away. And shit.

This song is so popular that it has been featured in concerts, Project Diva games, a stage play. Also Toraboruta-P announced that on April 17th 2012 he will release his novel entitled "Kokoro"; a novel based on the song. The novel is written by Toraboruta-P himself and illustrated by Nagimiso.SYS; illustrator most notable for his PV of Meltdown. The price will be around 1,260 yen and is available for purchase in Amazon on April 17th.