Talk:Four Archangels/@comment-32252462-20200108150210/@comment-3211055-20200108164324

As complicated as it seems, there are several plot points that you need to know.

In early story (just right after Ayase first confrontation with Gambiel), Yachiyo stumbled upon Yamato and she has been following him since. Their bonds is kind of mentor-student, especially considering the slightly chuunibyou Yachiyo.

Sakura, well... she has a somewhat unhealthy obsession with her twin (borderline yandere if you may) since her original motive is to find Yachiyo and take her back home. Gaining additional power from the Dingir only makes it worse.

As for why things turned out like that, Sakura just happen to found out about Yamato-Satan (and his relationship with Yachiyo) from Ayase and went out to his place to arrange the eventual meeting between the parties involved since she knew that Yachiyo is going to look for both of them eventually. So, Satan is technically just a convenience for Sakura.

tl;dr this is all Yachiyo's fault.