Japanese can be difficult to translate because of the way it uses pronouns, but it also has some special tricks that come in handy when you're writing a song about mirror images where there are multiple "I"s.
The way this song's lyrics are written, when the narrator is referring to her mirror double, she calls it わたし "watashi", "I", but this word is normally written 私 instead of in hiragana わたし. I guess this was done to give the word an unsettling vibe. Anyway, because of this, I used "i" instead of "I" the two times the word is written that way in the lyrics.