Thanks for the chapters.
I've honestly forgotten the plot outside the fact that the monsters are weird bio-weapons from the future.
Well, this one's more complicated so you might wish to reread at least from the beginning of season 2.
But long story short, there are two main plot lines. In one, Minji and Yun-yeong are trying to find and defeat the new "Mother", the monster who is leading the invasion of the present world by the predators from the future with the goal of killing all humans and seizing this world for themselves. In the process, they hope to rescue the soul of Minji's cousin, currently fused with a predator kept captive by Mother's faction. Mother herself seems to be a former friend of Yun-yeong's who went crazy about reviving her murdered family.
The other plot line is a mysterious human organisation that seem intent on enabling the invasion, and who have been experimenting on humans and predators. Their goals aren't clear yet.
Wild cards are Jeongtae, a human who knows more about predators than anyone else and who seems to want to prevent the invasion, but whose ultimate goals are unclear and whose ruthless methods irk Minji and Yun-yeong; and Minji's brother Min-ho, who is currently hosting some sort of parasitical predator who's protecting him on Mother's orders.