After Satoshi’s abusive aunt is murdered, Satoshi is, of course, the primary suspect. In order to protect him, Shion reveals she has been pretending to be her twin sister, Mion, this whole time. As a result, Shion is summoned to the head of the family for punishment; as she was never supposed to return to Hinamizawa. Despite taking her punishment, Satoshi still vanishes and Shion is heartbroken. Now, it’s 1983 and Keiichi comes to town.
Shion has gone mad with grief and is convinced Satoshi is still with her somehow. Now, with this backstory, I can understand why Shion is crazy and seriously pissed off. Her and Mion come in direct conflict with Mion trying to be loyal to the family and Shion demanding answers about the disappearance of the man she loves. We don’t get to know exactly what happened to him but Shion is NOT playing around. She sees Mion has even the barest interest in Keiichi and she’s using that to get as mean and dirty as her family was with her. I can’t want to see what happens next. 4 out of 5.