I feel like Marco would be such a good yandere. Something sore from all the fucking ? A wound from overdoing it? His talon made you bleed? his flames will make it go away and you will feel more relaxed in no time.
He is taking such good care of you pretty bird. There's no reason to leave.
/nod nod/ 100000000%
I really think it'd be almost impossible for you to realize he even is one unless something goes bad.
Crocodile, in his own way, gives you a chance to leave. He doesn't hold back - you can and will get a very unsettling feeling around him that leaves you feeling hunted. He's not letting you go if you cross the line and lay yourself between his teeth, but he does give you a chance.
Shanks, I think, doesn't hide how desperate he is for you, and if you catch on that's just a shame - unlike Crocodile, he doesn't give you the chance to run, but! you might not ever pick up on it. If things go smoothly for the most part, Shanks' affable nature will keep you from ever picking up on it.
But Marco?
Chances are he's decided you're staying with him before you've even heard his name. Whether you're an islander, or a new member of the crew, his mind is made up the moment his eyes settle on you. Call it instinct, call it insanity, he doesn't care.
And his touch is feather light.
Marco, Kaku and Sabo - given the chance - will have you desperate for them to the point that you might worry you're the yandere in the relationship.
But where madness might slip up Sabo, and where impatience might trip up Kaku, Marco steps through effortlessly. Unless you catch him tearing someone apart for daring to lust after you, you're just not ever going to know.
Find his journal? His feelings for you are that intense, but he writes them down to keep them in check. None of it's real, pretty bird, it's all role-play stuff to keep himself under control, don't fret it. Maybe you'd like to try role-playing some stuff with him so it doesn't seem so strange to you?
Hear someone talk about how he knew you were his before you'd even held his hand? He was just manifesting the reality he hoped to see. Sorry if it sounded a little intense, the guys tend to exaggerate things on top of it all. You know pirates and their fish stories, yoi. He was right though, and thank the seas for that because he's so smitten with you, he wouldn't know what to do with himself otherwise.
How... lucky for him... that you fell for him like you did.