You and Ace went to his brother Luffy's ship to socialize a little and for Ace to catch up. In the meantime that you two were there, the Straw Hats were already suspecting what was likely, that the two of you had a hidden relationship, and that neither they nor Luffy knew, but they gave it away

Until Ace pulled you into the kitchen to spend some time alone, and in the meantime, you ended up sharing some kisses and so on... You and Ace were almost kissing, just inches away... Until Luffy enters the kitchen in search of food and sees you two... Almost kissing..

Luffy: Ace?!