Zoro is a cambion, which means he feeds on sexual energy. A small crew like the Strawhats, its not normally enough to keep a cambion satisfied, but Sanji happens to be an abnormally sexually driven cook so it usually works out okay for Zoro. At least, it works out alright until Sanji finds out that Zoro's been taking energy from him through his dreams. For Sanji, he's trying to wade through the confusing mess of emotions for a certain marimo after a surprise kiss on the battle feild. It's not easy to do on a normal basis. It certainly isn't any easier when the man he has deeper feelings for is a cambion. Then everyone learns how important it is to keep their local cambion fed, for if they don't, someone might get eaten. literally.

Zoro and Sanji are fighting. And that’s not really a surprise, exactly, because Zoro and Sanji are always fighting. But it’s different, this time. This time, it’s not physical, and Sanji isn’t up in Zoro’s face yelling and screaming and calling him names. There’s no swiping of polished katanas against the lithe swing of powerful legs. It’s not physical combat. This time, Sanji’s fighting with silent avoidance and quiet resignation. This time, their entire nakamaship may be on the line. And this time, Zoro doesn’t know how to fight back. OR There’s something wrong with Sanji, but Zoro doesn’t know what it is or why it’s happened – why they’ve suddenly stopped brawling and hating each other left, right and centre. All he knows is that he has to fix it, or this Sanji – the Sanji that’s sunken and tired and so, so sad - may never go away.