Alfin's blood.
A fluid that has interested many in the mutation domain, so for Reina, it won't be bizarre that she would be interested in it.
Because at the end of the day, she was one of the lead researchers in cloning. Or so she claims. Whether it was the truth, only those from 500 years ago would be able to confess her validity.
"I wonder where Miss Reina learned about my genetics," Alfin asked, curious about how this woman obtained such crucial information about him.
Though, if one were to consider where she had been active in her free time, it wouldn't be too bizarre.
He had learned about some sort of camaraderie forming between Reina and Farsight. Which would make it easier to know why she might have been aware of this fact.
And with Reina's next explanation about how she learned about it from Farsight in a small conversation. Alfin got even more sure that his assumption was pretty much on point.