User blog comment:Servant of Evillious/Lunacy Novel Tidbits/@comment-69.115.21.210-20130904055746/@comment-6192846-20130904114259

From my perspective, it is supposed to be the point in the song where he is "made fun of" by her, as well as when the engagement between Sati and Gumina is revealed to Cherubim, the day before he slaughters his family.

My understanding is: Gumina wants to kill Sateriajis. Sateriajis wanted to kill Cherubim because he grew suspicious of Gumina and Cherubim's relationship. To ward off Sati's eyes, Gumina openly mocked Cherubim so witnesses could see she wasn't that close to him, while hiding her own intentions. Cherubim is heartbroken and we know the rest.