It wasn't just his appearance. No. Mainly his personality who got you so attracted to your captain's brother. Luffy has found him in the middle of the trip and now, Ace was traveling with the rest of the crew for some days.

You just observed him and exchanged some glances, but words? You weren't capable to speak at him. You would always get too flustered.

One day, you were walking out of your room, slighty yawning and stretching arms when you bumped into someone. That someone, was Ace.