Never Again to Mourn a Lost One

Happiness. This homeland was once joyful and carefree! But anything can happen, and this homeland was no exception. Ever since Happiness developed the "Dark Core," everything changed. This place gradually turned into a wasteland, while the invaders, like locusts, slowly devoured the last of its peace. Under an utterly absurd pretext, they tried at any cost to uncover what they believed to be a "secret that threatens all of humanity"!