You never take the reverse pill. You fully embrace being "Kaori" and marry Takeshi. The X-Change R becomes permanent. Soft Ending 2 (Return to Lab): Dr. Shinjo helps you reverse the change, but you remain emotionally scarred. It's a bittersweet "back to normal" ending.
After Day 3, the game splits into three primary routes based on your dominant stat. Here is the walkthrough for each. x-change r walkthrough
This is the first "Flag" moment. Selecting Asuka leans the story toward the "True Lover" path. Selecting Natsumi opens the "Forbidden Romance" path. Selecting Megumi usually leads to comedic side routes or specific fetish scenes. For a standard "Good End," choose Asuka . You never take the reverse pill