The cause of it all was that despicable blond outsider, Lord Green Otto, who, after arriving in Yae Village, discovered that Lord Miki God—the ancient tree before the shrine that Yae Village worshipped—possessed miraculous power. So he plucked one of the seven golden flowers blooming upon it.
This caused Lord Miki God, who protected Yae Sakura, to lose its power and become unable to safeguard the villagers of Yae Village as before. Later, the blond outsider returned, bringing with him an unknown calamity—the common viruses Westerners had carried to the Americas, which became incurable plagues to Americans who had never encountered them.
Yae Sakura, the Miko who worshipped Lord Miki God, believed it was her fault. Thus, she prayed day and night in the shrine until she finally collapsed there.
With Lord Miki God's help, Yae Sakura survived. But when she regained consciousness, the villagers of Yae Village were either dead or gone.
To keep Yae Sakura from breaking down, Lord Miki God erased her memories of Yae Village, then transformed the remaining six golden flowers into six younger sisters identical to Yae Sakura—First Sakura through Sixfold Sakura.
What struck Mo Yi as especially absurd and memorable was that First Sakura through Sixfold Sakura all possessed special abilities, each corresponding perfectly to the abilities of the Calabash Brothers. For instance, the eldest possessed immense strength, while the second had clairvoyance and super hearing.
After some investigation, they finally discovered that the enemy bringing the Honkai Beasts was actually Seventh Sakura, transformed from the golden flower plucked by that despicable outsider long ago—appearing as Theresa's Sakura Flame Waltz.
Because Lord Green Otto had plucked her before she matured, she was unable to grow up and was frail and sickly.
Thus, Lord Green Otto forbade her from going outside, afraid that something