If I'm thinking of the right one, you unlock it by using the cat costume a few times :)
it worked, thanks ! also would you know if it is possible to unlock all haato naked cgs (the one with a vibro and others) on one run or some cgs are restricted to some routes ?
You're welcome ! :D The ones unlocked in foreplay mode? They can all be unlocked in one run, if I remember correctly :)
