This is an ABO world full of unknowns, where children's glands begin to develop at the age of ten and differentiate at the age of fifteen. Cui Ran has been determined to be a top A since he was ten years old, but unexpectedly when he was separated at the age of fifteen, his gland (mark) was bitten by Fu Chen, who was already separated at the age of sixteen, in front of the whole class. From then on, he embarked on the long journey of O's potential...
Purpose: Novel