When you got 100% achievement.Use weapon "curse dagger" defeat all monster again.Then press "Esc",choose "back to title screen",Then click "load game".You will see compete >100%.If you think its too hard.Just add this pointer address into cheat engine and set value to 107993014 when you fighting with Monsters,you will auto victory.
Pointer Address:"Monster Girl Incursion.exe"+00769570 offset1=128 offset2=198 offset3=14 offset4=20 offset5=24 offset6=10 offset7=3C offset8=4