For starters, you MUST make sure that the girl you want to romance CAN be romanced.
You can do this by making sure she is a "Confidant" or "Social Link" or look at Sub Step 3.

Once you've confirmed that you can romance the girl of your choice you MUST level up their Social Link to rank 8-9, this will allow you to be able to romance them.

Once you've leveled up their Social Link to rank 8-9, you will be able to romance the woman, you do this by progressing through the event like normal UNTIL it says "I should choose my words carefully.."

After that, if you have already romanced another girl it will say as shown below, "I'm already in a relationship with another girl..."

But if you ignore that and move on to the options of dialog you can choose, if you play it bold, depending on the woman, you will succeed in romancing her.

IF YOU ARE LOOKING FOR A SPECIFIC ROMANCE OPTION LOOK AT SUB STEP 3

• Ann Takamaki - Romance option unlocks 4/15 (main story), Rank 9 Social Link needed
  
• Makoto Nijima - Romance option unlocks 6/25 (main story), Rank 9 Social Link needed
  
• Futaba Sakura - Romance option unlocks 8/31 (main story), Rank 9 Social Link needed
  
• Haru Okumura - Romance option unlocks 10/31 (main story), Rank 9 Social Link needed
  
• Tae Takemi - Romance option unlocks 4/15 (manual unlock), Rank 8-9 Social Link needed
  
• Sadayo Kawakami - Romance option unlocks 5/24 (manual unlock), Rank 8-9 Social Link needed
  
• Hifumi Togo - Romance option unlocks 6/25 (manual unlock), Rank 8-9 Social Link needed
  
• Chihaya Mifune - Romance option unlocks 6/22 (manual unlock), Rank 8-9 Social Link needed
  
• Ichiko Ohya - Romance option unlocks 6/23 (manual unlock), Rank 8-9 Social Link needed
  
• Kasumi Yoshizawa - Rank 1-5 romance doesn't exist, progress to the third semester to unlock romance option, 12/8 (Main story), Rank 8-9 Social Link needed.

Good luck and go get em'