秘蜜〜黒の誓い〜 (Himitsu ~Kuro no Chikai~)

Background
The meeting at night, would eventually lead to an unforgivable sin. A pathetic fallen angel, a human girl, the forbidden fruit, love and allurement, and a deadly betrayal, all in this one tragic love story. The song tells of the angel Rin, that stumbles upon a girl, Miku Crynpto, who Rin instantly falls in love with. But, love between an angel and a human is forbidden, and Rin yearns to find a way for them to be together. She kisses her and dissapears in shame. Afterwards Miku meets a mysterious boy named Len, and falls in love with him. Although she is to be wed to another man, she left with Len. But, another angel, Kaito, Rin's old partner has been sent to punish Miku and kills her. Len reveals himself to be Rin, having given up one wing to the devil to be with her. She gave up her last wing to save the Miku, sacrificing herself and leaving a single feather.

This song is featured in the EXIT TUNES compilation album "Vocalonexus" and is featured in Hitoshizuku-P's mini album Himitsu ~Mushoku no Chikai~; with an answer song explaining the girl's point of view, and both are featured in Hitoshizuku-P's album; STORIA. It is also featured in Yamashizuku's debut album EndlessroLL.

Publications
A novelized version was published on September 24, 2012, with much more characters. A book signing was also available with Hitoshizuku-P and Suzunosuke attending on September 29. A book trailer can be seen here.