[ His surprise doesn't go unnoticed, but at least he appears to take it in stride. Which... good. Again, she nods. ]

That's the simple explanation, at least.

[ Koharu turns the pistol around in her hands, as if inspecting it over while she speaks. ]

If we choose the right target, they will, but it depends on if their likes and preferences are compatible with the person we've decided they would love. So, basically—if 'person A' would've never had any interest in 'person B' no matter what, shooting 'person A' would be ineffective.