WARNING: The following contains spoilers for Episode 3 of Higurashi: When They Cry - Sotsu, "Demon Revealing - Part 3," now streaming on Funimation.
Rena’s descent into L5 continues to skew her perception in Higurashi Sotsu, with the intense paranoia brought on by the disease turning her against one of her closest friends in Episode 3. As things continue to fall apart, Satoko watches over Rena ensuring the fragment’s failure with Rika none the wiser, and spurred on by suspicion and misconceptions, Rena makes a fatal decision concerning Keiichi.
Paranoia eating at her as she continues to dispose of Rina’s body in the episode, Rena digs a hole in the forest to hide the pieces of it, though she is still able to maintain her usual joyful front with the club members. In the days leading up to her attack on Keiichi, Rena becomes increasingly suspicious of him. Eventually, various misunderstandings coupled with the worsening effects of Hinamizawa Syndrome convince Rena that Keiichi knows something about Rina’s murder.
Things only grow worse when Ooishi asks to speak to Keiichi at school. Rena watches the two from a nearby window and knowing that Ooishi is a police officer, suspects that Keiichi is working to have her arrested for the murder -- further agitating her. Satoko, who runs into her, seemingly takes pleasure in the situation at hand.
Rena's feelings of insecurity come to a head when Keiichi later talks to Ooishi on the phone and the conversation is played out through Rena’s perspective this time. Keiichi expresses his surprise over Rena’s past troubles with the law, leading Rena to assume Keiichi is referencing Rina’s murder and runs out of his home in a panic.
Now convinced that Keiichi knows about the murder, Rena decides to get rid of him. But on the night that she leaves to do so, Rika watches her and Keiichi interact outside of his house, optimistic at Keiichi’s chances of overcoming his uncertainty while completely oblivious to Rena’s intentions. In a dark twist, she cheers the two from outside, unaware of the violent struggle happening inside the Maebara household.
Satoko and Rika learn of the attack along with the rest of their classmates the next day, and when Chie tells everyone that Rena didn’t survive her wounds, Rika storms off with Satoko not far behind. Having proclaimed that the current fragment has failed, Rika decides to move on to the next one. Satoko finds her corpse soon after and briefly taunts her before following suit.
The end of Higurashi's “Demon-Revealing” arc gives viewers the complete picture from Rena’s perspective along with Satoko’s role in the tragedy. It will take some time before Sotsu gets to the events of Gou’s “Cat-Deceiving” arc, but seeing Satoko so indifferently sabotage her friends certainly isn’t painting her in a sympathetic light. The upcoming “Cotton-Revealing” arc might just be much of the same, with Sotsu’s retelling of the “Curse-Deceiving” arc a potentially pivotal moment for Satoko’s character going forward.