Pink, Paperback

Yumiko moonlights as a call girl because her day job doesn't pay enough to feed her pet Croc. Haru an aspiring writer who has nothing to say, sleeps with a woman his mother's age not just for the money but to work on his "powers of observation." So when Yumi's step-mom turns out to be Haru's sugar-mommy, it is time for shenanigans. A little bit of drinking, a little bit of blackmail and a visit with Croc is enough to change lives and maybe add some color to a comfortable but bland life.
Daddy kept Keiko's mom as a pet; she keeps Haru as a pet; I keep Croc as a pet... I Yumiko someone else's pet Is she willing to let someone care for her like that?