Seven Deadly Sins

The Seven Deadly Sins (七つの大罪 Nanatsu no Daizai) series is a series of songs made by mothy, also known as Akuno-P. The series is currently slated to have at least eight major components.

Background
The series focuses on the "cardinal sins", the vices used since ancient Christian times in order to instruct on the morality of humanity. While more minor sins, "venial sins", could be easily forgiven through sacramentals, the cardinal sins would lead one to eternal damnation if not absolved through Penance or perfect contrition.

The theme is common in Catholic tradition. The definitions have changed throughout the years, but there is a general agreement on the current seven with their current Latin names.

Heartbeat Clocktower (ハートビート・クロックタワー)
Sung by Kaito "Heartbeat Clocktower" was not the first of these songs to be released; it was released April 25, 2010, long after many of the songs had been released. However, it serves as an overarching theme for all of the songs, as well as establishing a background. It is the fourth song in the "Clockwork Lullaby" series.
 * [Nicovideo broadcast http://www.nicovideo.jp/watch/sm10512919]
 * [YouTube broadcast with English subs http://www.youtube.com/watch?v=89JM75GxpfQ]

The song concerns a mysterious clocktower and its guard. The dead owner, the "Collector", created a "Theater" and dolls, "Collectibles", with life to inhabit it - they forever enact their story, while hapless visitors end up prey to the "Master of the Graveyard". The "collectibles" are presumably the representatives of the seven sins. The "Graveyard" is the "hellish yard", while the court is the "heavenly yard" ("the heavenly yard" is the name of Akuno-P's blog). The former guardian of the clocktower, which keeps the theater running, had been the embodiment of greed; the current guardian, realizing that the clock was going to stop soon, sacrificed himself to keep it running by taking out his own heart and using it to power the clocktower.
 * Main article and detailed information: Clockwork Lullaby

Superbia (Pride): The Story of Evil
Various songs, sung by Rin Kagamine, Len Kagamine, and Haku Yowane

A subseries of the Seven Deadly Sins songs, the first song of the series was uploaded on April 6, 2008. The songs concern a kingdom ruled by a princess who, on top of being tyrannical, became jealous when the prince she fell in love with was in love with another girl and fueled this by destroying an entire kingdom and the women in it. Her brother, her servant, is also so loyal to his sister that he will kill in order to keep her alive. She ruins the lives of many in order to keep her own goals alive - and is forced to become repentant when her brother finally sacrifices himself for her.
 * Main article and detailed information: Story of Evil

Gula (Gluttony): Repulsive Food Eater Conchita (Akujiki Musume Conchita/悪食娘コンチータ)
Sung by Meiko, backup by Rin Kagamine and Len Kagamine The song was uploaded on March 3, 2009. The song concerns Conchita, a woman who, at one time, ate only the most delicious and exquisite food. Now, however, her tastes have evolved so that she wants something new and grotesque every day, and nothing enters or leaves her palace. The fifteenth personal chef of the year asks for a brief vacation, but she, angry, decides to eat him. Running out of food to eat, she ends up eating her butler and maid, and when everything has gone, she ends up eating herself - which nobody else will ever know what it tastes like.
 * Nicovideo broadcast
 * YouTube broadcast with subtitles

Invidia (Envy): The Tailor Shop at Enbizaka (Enbizaka no Shitateya/円尾坂の仕立屋)
Sung by Luka Megurine The song was uploaded on December 7, 2009. The song concerns a tailor in the fictional city of Enbizaka (enbi = envy), one who is known for her skill. The only thing she thinks about most of the time is the fact her "love" is unfaithful and does not come "home". She sees him walking with a woman in a red kimono and murders her with her tailor scissors and takes the kimono, acting as if nothing had happened and that she is concerned about the rising murder rate. She later sees him with a girl in a green sash and does the same to the girl, taking the sash - the same happens with a girl with a yellow hairpin. The tailor dresses herself in the kimono, sash, and hairpin, thinking that she has made herself beautiful for him. But as it turns out, the man does not even know her; the three females were his wife and daughters, and so when he meets the tailor, he does not recognize her. Offended at this apparent lack of acknowledgement, the tailor murders him, too, and carries on with her work.
 * Nicovideo broadcast
 * YouTube broadcast with subtitles

Luxuria (Lust): The Madness of Duke Venomania (Venomania Kou no Kyouki)
Sung by Gakupo Kamui The song was uploaded on July 25, 2010. The song is about a man, "Duke Venomania", who, in his childhood, had been mocked and teased by others. In adulthood, he made a deal with the devil to be irresistible to women. The women now flocking to his house create a harem for him. One of these women happens to be the one who "made him for a fool", his childhood friend. However, a jealous man who had lost his wife to Venomania came to his palace, disguised as a woman, and stabbed him in the chest. The charm now broken, the women flee from his palace, and as Venomania dies, he sees his childhood friend, and reveals that he had truly loved her.
 * Nicovideo broadcast
 * YouTube broadcast

Avaritia (Greed): Unknown Kaito song
"Heartbeat Clocktower" revealed this song would be sung by Kaito; however, nothing else is known.

Acedia (Sloth): Unknown Miku song
"Heartbeat Clocktower" revealed this song would be sung by Miku Hatsune; however, nothing else is known.

Ira (Anger/Wrath): Unknown Gumi song
"Heartbeat Clocktower" revealed this song would be sung by Gumi; however, nothing else is known.