The first penetration scenes were implemented in 0.6.10 in form of the level 6 level-up event.
In January starts the 0.7.x update cycle, which means that there will be more dirty things in the future.
You have to visit the spa on Saturday at 10am with M&S first.
The M&S spa event triggers at home.
Miss Tyler's level-up event should trigger at M&S level 6.
Visit her at 3pm in school again.
If you really missed the USB drive event you can go to Cheats and "give you previous items".
The spa events advance with corruption levels. (for M&S)
Level 1 -> Level 1 Spa event
Level 2 -> Level 2 Spa event
and so on...
But you can play all side character events when visiting the spa alone in level 1 already.
In order to level up you have to play crucial events with M&S.
Those events are the weekend dates (triggers on Saturday and Sunday at 10am in M&S rooms - "Go Out")
Cosplay Events -> Buy Costume in Shop
Lingerie Events -> Buy Lingerie in Shop
After all that is done, you're able to level up at dinner.
There's also an in-game walkthrough