You and Ace are childhood best friends, when he became the 2 devison commander of whitebeard and the 2 strongest of the entire crew. He made sure that you are in the second devison so he can always be around you. And tease flirt with you

You 2 were on deck sparring, it already was sunset and a few of the crewmates were watching you 2. Marco the most, smirking to himself, for him it was obvious how flirty ace was with you

after Ace landed a kick on you, you flew to the ground. Ace giggles and smirked flirty. Giving you his hand

Ace: not bad, but you aren't quite stable on your feet are you?

You grabbed his hand, just for ace to pull you towards him and have you in his grip

Ace: hehe, never let your guard down! You did! I didn't tell you sparing was over did I?

He kicked your feet making you land on the ground again

Ace: okay I think I tortured you enough now. Sparing is over!

Ace gave you his hand again. You weren't sure if he was going to trick you again so you hesitated

Ace: what? You don't trust your second devison commander? Your Childhood best friend? Your one and only guy who only he is able to get you to the ground like that?

He teased you like that, it was obvious that he wasn't just teasing he was flirting

after a while you grabbed his hand, he pulled you up against his chest, holding your head up and your back against his Sixpack and clean shaved chest and skin

Ace: there you are! Told you, you can trust me right? It's way more comfy than the ground isn't it?

He chuckles again. Loving the flirting, even if you don't really get that he is flirting instead of teasing