Originally Posted by Firzin
Judging by the preview it looks like they skip chapter 16 of the manga D:
They might bring it back in a future episode or maybe it just wasn't shown in the preview. The last episode didn't go in order of the manga chapters but it still following what happened in the chapters themselves. Yukimura would have shown 'himself' and joined in Ep 3 if it followed the order since 'he' joins before they go to the pool in the Manga but he joined after in the Anime. A few other chapters have been skipped which I'm assuming they'll be thrown in another episode.