Sorry, but how can I increase lust above level 1?
By interacting with your personal notebook, you then click the ''Web Browser'', then open ''Naughty Nook'' website (in-game obviously) and scroll all the way down to ''Upgrades''. The heart icons are the ones you are looking for, each raising the ''Horny Level'' up by one permanently. As the ''Horny Spray'' stacks on top, boosting it one level further upon usage, obviously make sure you use it on the ladies for best results