Ancient Methods to Tame Magical Beasts

Pikeru is a newbie beast master and Marcoule is his summoned partner, a fluffy little critter. Over the course of a few months, they train together and Marcoule evolves into a big (but still fluffy) beast. Several times bigger than Pikeru in fact, with boobs to match. And it seems that together with her growth, Marcoule's libido has expanded too...