Uso x Mote ~Usonko Motemotation~

Main character moves to an academy with boys to girls ratio of 1:9. One day he meets a self-proclaimed flower fairy "Momo" who promises to make his dream come true. Without much thinking, he says he wants to be super popular with girls. That wish is granted on the condition that he can only say lies from now on.

[From vndbreview]