In truth, while An Jing was cultivating, Chenyinzi did provide some assistance.
Yet precisely because of this, he found it unbelievable.
The formation of the Mingjing Heart involved minor details and subtle techniques that mere manuals could not teach. Moreover, the personal experiences brought by Guangchen's possession carried a distinctly personal style—An Jing's meridian flow differed from his, and could not be entirely copied.
Chapter 439