This chapter feels mostly like a build up to something major, Oda is planning for the next chapters.
And with someone giving Luffy food and now Luffy being gone, Oda hints that there is something big, he is still hiding from us (If you want to know more of what it exactly is, Oda is hiding: Lucci is on the side of the SHPs and is going to face the WG soon.).
For this, Oda already sets the stage with Kizaru first. While many readers think that the admiral is probably going to change sides, Kizaru ultimately gives us the counterpart to the actual unrevealed protagonist (alongside the SHPs/Vegapunk) of the arc: Lucci.
Lucci is currently on the SHP’s/Vegapunk’s side and their strategist/chief of staff. His brother is Shaka and while he did follow his heart and decided to help the SHPs/Vegapunk for the reason of saving his family, Kizaru decides to do his duty and kill his friends/family in order to fullfill his mission. This way he acts as the antagonistic counterpat/role in contrast to Lucci’s protagonism. Oda is now building that up and I hope that you decide not to lay much weight into hoping that Kizaru will change sides here.
So, keeping that in mind, we already can deduct, who Oda meant, when he announced a fight between two characters, as the surprising battle between “[…] that person and that person […]” is going to be seen in the next few chapters. And this fight will take place between Kizaru (or Saturn) and Lucci (– a vampirized Lucci, since he was bitten by Stussy and has now become a vampire himself).
So, summing it up: Plot twist ahead.