As a Cat God, Shiratama possesses Yaya as his host. Yaya explains the reason why Shiratama possesses her is because they have a "good relationship". While it's said Cat Gods usually stay inside their hosts, Shiratama prefers to be outside of Yaya to play with her. Although Shiratama doesn't talk, Yaya appears to always understand him. The two care deeply for each other to the point that they think of each other's well being.
Like Yaya, Shiratama becomes quite attached to Kogarashi after being fed his grilled fish.