@enternal
An escort, generally speaking, is a prostitute.
Now this particular rent-a-girlfriend business doesn't sell sex, they just sell the illusion that a girl WANTS to have sex with you. In that regard, Chizuru's profession is more akin to a stripper, except she doesn't take her clothes off. That said, many prostitutes say their clients don't hire them for sex, but just for companionship. They just want to feel desired and have attention paid to them because they are lonely.
As far as the "two steps forward, one step back", it's really more like "one step forward, one step back." Despite the author claiming that little by little their relationship is progressing, it's really not any different than it was almost a year ago. And, any progress than HAS been made... well, there's really no reason for it to have occurred, because there's no reason for any of these girls to like him.
P.S. Where's Ruka?