The only titfuck scene is currently for Fern. After some days your aunt(?) will come to your house in the morning and will tell you the carpentry shop is open. You have to go to there which is in a commercial district and talk to Fern at the desk and ask for maintenance. For the next week she will come to your house until 8pm. While she is working you cant talk to her and gain trust. At 6 you can talk to her and ask for "service" which is the titfuck scene with a shirt. increase trust/lust with beers and redoing the service to get the shirtless option
tldr: unlock fern and interact during maintenance and ask for services 6-8pm. you can gift her beers for more trust