Touhou Kikeijuu: Wily Beast and Weakest Creature

Beast spirits began to invade from Hell en masse.

"They're trying to take over the surface world with brute force and sheer numbers. I beg of you! Venture into Hell with me, and put a stop to their plans!"

So she was told, by a beast spirit that was cooperative with humans...

Reimu, Marisa and Youmu encounter several animal spirits from Hell, who claim that their fellow animal spirits are plotting to take over the surface world. The three heroines team up with the spirits, and venture into Hell to take out this new potential threat.