From The Start

"Hua Cheng remembered.
He remembered the sensation of being weightless as he fell down the terrace. Life had never been precious to him, so why should he have cared if he did fall or not? In fact, he should have welcomed the fall... But his traitorously selfish heart resisted.
He remembered not wanting to die, solely wishing for a chance to get to know the boy clad in white robes better.
His wish had been fulfilled- that very boy had caught him in his arms. He held him, as if he was something precious. As if he was someone worth saving.
He remembered an odd warm feeling blossoming in his chest, spreading to every part of his being until he was all giddy and light headed.
He remembered Xie Lian and his beautiful smile."

or

When did Hua Cheng fall in love with Xie Lian? It was difficult to answer. His love and devotion was all consuming and never ending. Everything that Hua Cheng was today, everything that he strived to become in the future, all of it was driven by his love for Xie Lian.

But perhaps, the beginning of this extreme obsession could be traced back to his childhood and four encounters in particular
Four encounters, and four stages of him falling hopelessly in love.