Tony:
Tony appears only three times in the game. The first is on Day 8 when you go the office. You will have some different dialogue that happens during the scene if your Desire with Serena is 99 and lower or 100 and higher. Around day 15 or 16 at 18:00 (if your desire is 149 or lower), go to Serena’s office and look for her. There will be a small cut scene (if you interrupt it you will receive -40 Desire). Also, on day 18 if your Desire is 199 and below with Serena, go to her office and look for her. A small scene will play out and you will get ending 12 (regardless if interrupt it or not).