The title is a reference to Ilka and her serial number (OPCI_2404_IL).However, its average note per second (9.635) is lower than that of Floor of Lava (10.471).The Chaos chart of this song has the most amount of notes in Cytus II, 1773, beating Floor of Lava by 150 notes before it was beaten by Fur War, Pur War by a total of 227 notes.The intro to L can also be heard in the background 39 seconds into the song.However, many of the note patterns from the L series show up in the Chaos chart.
This is the only song along with Syten, conflict and THE BEGINNING which uses different versions for the difficulties. This is the longest song in Cytus II, beating the previous longest song, V., by 3 minutes and 26 seconds. It can be referred to as a spiritual sequel, though, as the title, song, and chart share similarities to L. This song is in the album 'Rayark 10th Anniversary Concert Collection' available on most music platforms. According to Ice, this track is not a sequel or related track to the original L series.As of August 2020, this song is no longer available in Chinese localizations of the game because Ice announced his support of the Taiwan Freedom Movement.Purchase the song pack "Emotion Samples 01" in the Black Market.