I'm Actually the Last Cultivator

In this world people cultivate toward immortality in stages, and the Tribulation stage is the highest of them. Anyone who has reached it has no equal. Qin Sheng, a Taoist on Ziyun Mountain, reached it long ago. His master decides his student's character needs work before his pride gets ahead of him, tells him he is an ordinary man, and sends him down the mountain to live among ordinary people as a Taoist priest. Qin Sheng takes this at face value. In a hidden realm he ends up saving, more or less by accident, a young woman of good family named Yang Qin who is in trouble. She takes him for the Holy Son of that realm and willingly becomes his wife. The two travel together and get into one dangerous situation after another, and he handles each one while still thinking of himself as a run-of-the-mill Taoist. Along the way he comes to think that cultivation is mostly a matter of training the heart. He also begins to notice that his own strength does not match the story his master told him.