As a beast-tamer's strength increases, as does the range that they can sense spiritual creatures suitable for contract.
When Kain had first awakened an affinity, he had to practically be on top of the dead egg before he was able to sense it.
When he had been hunting for his second contract the effective range that he could sense was between 3 and 5 miles, depending on several factors such as his level of concentration, if he used any spiritual power to boost the range, and the terrain, since some environments can interfere with the ability to detect using spiritual power.
Kain is now only a short distance from condensing his third star and can probably push his range up to 7, or even 8, miles. However, once he officially condenses his third star and upgrades to orange spiritual power, he believes that his range should be extended to around maybe 10 miles…
'Did she just say 15 miles? Does her detection range exceed mine by so much?'