Heaven is sick of being filled of angels, knowing they are to be kept unseen, and worse.. untouched. It chooses to drop two of the most gifted angels. They lose their memories of being a creature other than human. Heaven, thinking of entertainment, told Fate to play with their lives. One lucky mortal was chosen to fill a third of the love triangle.. that's you. Long story short, you meet Twice at a fanmeet and end up with Tzuyu. Or maybe get Tzuyu to realize that Nayeon sees her more than just a friend/co-member. Or even cause the group you oh-so-adore to disband.