As Nathan said, he was training with Charlotte for the next three days.
Fenrir got bored because he had nothing to do, so he didn't bother to accompany Nathan for the next three days.
On the other hand, Anubis did his best to learn this technique. Even though he was a Divine Beast and his control over Ena was quite good, he struggled a bit learning the synchronization.
He had never done something like that, so it was just him learning from scratch.
Fortunately, his foundation was extremely high. He could master the technique in two days. At the same time, it didn't change the fact that his Ena wasn't high. All the Ena came from Nathan, so he had to be patient to utilize the true power of this synchronization, at least until he got more Ena.
Still, the one who improved the most was Nathan. Nathan might not have a high absorption rate, but that didn't mean his talent was bad.
