What made Sakuya decide to switch sides?

Question

In Rewrite, Sakuya, Chihaya's butler, is nothing but antagonistic towards the protagonist Kotarou from the moment they first meet. He calls him insulting names and is generally just a bit of an asshole. It later turns out that both he and Chihaya are working for Gaia, the eco-terrorist group who want to destroy all human life

(and who ultimately succeed in the final episode of Season 1).

Then, around Episode 8 or so, he randomly shows up in the magic forest and saves Kotarou's life. He announces he's now working with Kotarou and friends against Gaia, offers to train Kotarou, and becomes considerably less antagonistic towards him. Absolutely no explanation is given for this, and to me it seemed to come completely out of left-field.

What prompted Sakuya to change sides like that so suddenly? I think Chihaya may have already defected by this point, but surely that can't be the only reason?

Answer 1

I don't remember what exactly happen in anime, so I will talk about Sakuya in VN.

Sakuya's loyalty lies completely with Chihaya. And Chihaya is not that loyal to Gaia. In her VN she gives up on Gaia few times. And Sakuya always follows. And while Sakuya does insult Kotarou, it is mostly playful messing around. He never really endangers him. He is basically trolling him, because he knows he gets reaction out of him.

Why Sakuya doesn't like Kotarou is explained in the VN:

Sakuya is same as Kotarou, having the Rewrite ability. And like Kotarou, he abused it to the point he lost his humanity and became a familiar. And he simply sees himself in him and doesn't like to be reminded of his past. But when situation gets serious enough, he puts all joking aside and begins treating Kotarou properly.

tl;dr; Read the VN. The anime is terrible, TERRIBLE, adaptation.