Berserk Button: Shion was relieved when Kimiyoshi told her that she would be forgiven for breaking the rules and visiting the forbidden shrine storeroom. However, Kimiyoshi explained that this was because "she was different from that Houjou brat" (referring to Satoshi). In a fit of rage, Shion knocked him out and locked him away in the Sonozaki basement.
Better to Die than Be Killed: Rika eventually comes to realize what scenario she is stuck in this time, namely Shion getting infected with the Hinamizawa Syndrome and going on a Roaring Rampage of Revenge as a result, due to having already experienced these events in Watanagashi-hen. Seeing how Shion gruesomely and slowly tortured her to death last time, Rika decides that she would rather not go through the whole torture part again, and opts to kill herself with a kitchen-knife instead.
Card-Carrying Villain: Deconstructed with Shion. After Shion mercilessly murders Satoko, she recalls a promise she made to Satoshi: to look after his younger sister. While she does feel terrible remorse, she eventually marvels at the idea of being "completely demon". Shion plays the role of a sociopathic, monstrous, and unforgivable demon for the rest of the arc, convinced that she has done too much wrong to ever be forgiven. Even more shocking to her is Keiichi's decision to forgive her despite everything she's done wrong.
Cold-Blooded Torture: Shion is subjected to such an ordeal when she is made to 'atone' by tearing out her own nails. Later on, however, she also performs these sorts of tortures to others, including her uncle Kimiyoshi and Satoshi's little sister Satoko.
Fingore: As a result of her love for Satoshi and her flight from St. Lucia, Shion had to take off three fingernails in order to protect the people who had helped her escape: Kasai, Yoshiro, and one other. This is still considered to be one of the most shocking and horrifying moments in the entire Higurashi series.
Green-Eyed Monster: Shion. Both literally and figuratively. Despite her best efforts to conceal her feelings, she secretly resents Mion for being groomed to take over as the family patriarch while she was made to become an outcast. It turns out that before she and Mion made a permanent exchange, Shion was actually the Sonozaki family heir. Shion envied Mion for enjoying a privilege that rightfully was hers, even as she felt horrible about passing it all onto her sister. As Satoshi disappears, Shion becomes even more jealous of Mion for being able to live with Keiichi, the boy she loves, but Shion was unable to do so because of her own circumstances. Shion asserts later that she could have rescued Satoshi if she had been in Mion's position instead, considering that Mion was the heir apparent and Shion was the social outcast.
Have You Told Anyone Else?: Turns out Shion pulled this on Keiichi, but she was admittedly a little more crafty about it than usual users of the line. When Mayor Kimiyoshi goes missing, she told Keiichi that she thinks it was her fault because she confessed to him about having been part of the break-in at the shrine storehouse, and that something terrible might have happened to him because of it. Keiichi panics and admits he told Rika, and now fears that something will happen to her too. As it turns out, Shion was the one who killed Mayor Kimiyoshi, and Keiichi ended up swallowing the bait and marked Rika as someone of interest to Shion.
Love at First Sight: The first time they meet, Satoshi rescues Shion from a group of thugs. Shion, who has been ignored and rejected by her family for much of her life, quickly falls in love with him. And on occasion, she may go too far with it.
Murder Is the Best Solution: In this chapter, we are shown how Satoshi killed his aunt to protect himself and his sister, Satoko, from more abuse at her hands. While Satoshi did save Satoko from their aunt, he soon vanishes after committing murder for reasons that no one could understand.
Perspective Flip: This episode show the events of Watanagashi-hen, as well as the lead-up to them, from Shion's perspective.
Twin Switch: Shion locks up her twin sister Mion and pretends to be her, successfully fooling everyone in their circle of acquaintances. As it turns out, though, this trope is considerably more important than originally thought. As children, Mion and Shion truly traded roles. Permanently. The true "Shion" is actually "Our!Mion," and "Mion" is actually Our!Shion. Being the younger twin meant that Shion was shunned by her family, while Mion was groomed to take over as head of the household in the future. While they are identical, the twins felt that they were being treated differently and made the decision to switch roles on a regular basis. But, one day Mion and Shion traded places permanently when the family imprinted the demon tattoo on 'Mion's' back.
