Fein didn't know why... He suddenly felt embarrassed because of the enthusiasm of the four S ranks. What they didn't know, he already rudely 'stole' their information and recorded their strengths and weaknesses in his memory palace that he could retrieve anytime and use against them. He could literally make use of the information obtained to counter their abilities in a targeted manner.
His probe ability looks simple, but it was actually Fein's most useful ability that would help him in his future battles indirectly.
But Fein didn't show it on his face. He casually squeezed out a natural smile on his face and greeted the four politely. "Nice to meet you, seniors. May I know why you want to meet this humble junior?"