Rain had always been guarded when it came to sharing his knowledge of secret techniques with others. This reluctance came from a combination of reasons, each of which had contributed to his initial hesitation.
Rain had learned over the years that trust was not easily earned. Many people he had encountered in the past had their own agendas, and sharing his secrets could potentially lead to those secrets being misused or falling into the wrong hands. He was cautious about revealing the extent of his abilities to individuals he couldn't fully trust.
The secret techniques he had developed were a source of advantage in battles and challenges. They set him apart and gave him an edge. By keeping them to himself, he maintained an element of surprise and unpredictability in his encounters. Sharing these techniques could potentially diminish their effectiveness.