7番目の僕 (Nana Banme no Boku)

Background
The song was first uploaded on May 12th 2010; and despite the fact that it's yet to reach hall of fame (exceeding 100,000 views) it is one of Mayuko's most notable work aside from her Grave-Sending Song series.

Many viewers from Nico Nico Douga were impressed over the seven voices of Len, some were confused thinking they're Appends; though at 2010 that time the Appends weren't present.

It tells a story of a boy (Len) who at first knew nothing of the world, but as time passes he changes his personality (and so does his voice and appearance) six times. There were ups and downs on his personalities, but when it came down to the seventh "me"; the seventh killed him (suicide; Mayuko's A/N said "with this hand")