This subject is a mistranslated title. This song is known as "My Seventh Celebration" in the Western fandom, but "On My Seventh Birthday" is more suitable. This tradition comes from Despair Media's mistranslated title. More subjects categorized here.
This subject is a questionable warning. This song's lyrics or video may contain questionable content such as: Violence, Suicide, view at your own risk. For further information see the discussion here and see more subjects categorized here.
Romaji: Watashi no Nanatsu no Oiwai ni
English: On My Seventh Birthday
Published May 21, 2013, with 90,300+ Niconico views, 900,900+ YouTube views, and 36,700+ SoundCloud views
The song introduces the two main characters of the series, the slightly-older Tsukuyomi and the slightly-younger Amaterasu during their shared seventh birthday, establishing their familial bond of being fraternal twins. While the two are very close, a petty dispute and accumulated hatred causes Amaterasu to kill Tsukuyomi by a blow through the abdomen with a staff.
While the illustration of the two sisters being impaled on the same staff may be misleading it can be inferred that it serves as metaphor for the consistent theme of the two "being one" as well as their eventual shared pain and confusion.
Part of masa's album ADULT, this version of Watashi no Nanatsu no Oiwai ni is a remake of the original song featuring much of the previous arrangement as well as new instrumental arrangements and lyrics.