Dolls become a common occurrence in human world. Their purpose is to calm and heal humans hearts.
As technologies evolved new type of dolls got constructed - "sub-dolls" who make the owner feel a wide range of emotions. You're the person who creates and trains dolls.

[From vndbreview]

In a strange world, our guy's master has to leave in a hurry. Now, he is going to be a full doll trainer. He gets parts from a secret shop run by his childhood girl, then a doll is put together using nanotech by his computer tree. It is up to him to train the dolls in different skills. He better hurry, since dolls only live 10, 20 or 30 days and it cost 2 million credits to put their age back to 1 day. The only way he can make big money is to sell a well trained doll.

[From Li's Fun House]