Poenitentia

Background
poenitentia, poenitentiae N F [XXXCO] regret (for act); change of mind/attitude; repentance/contrition (Def); penance

"Poenitentia" is an original song composed by Triangle -. According to the author, this song has no meaning and that they just wanted to do a quick thing with Hatsune Miku's V4X trial.