This song contains explicit lyrics and themes; thus, it may be inappropriate for younger audiences. The Vocaloid Wiki does not have a policy on lyrical content or theme; however, it attempts to follow the Wikia TOU. See Thread:68883 for further discussions.
This song is another work of Deadball-P, who often writes lyrics of dispute. The work also brought controversy on both Nico Nico Douga and Youtube. This song is often interpreted as Luka being a Nun, and is supposed to maintain virginity. But when she does have sex and is not aware of it, she hides her later pregnancy and gets an abortion. She is so paranoid yet in love with the man she had sex with that she thinks that everytime she has a period, she killed another child, like she did with her hidden abortion.
Luka's combination of her depiction, being a Nun, violating her celibacy (a vow never to have sex) as a Nun, and her committing abortion is considered immoral and blasphemous, most especially to people with Roman Catholic / Christian faith, where abortion is seen tantamount to murder. This is the reason behind its controversy. As a response, most UTAU voicebank authors prohibit covering songs like this.