I remember there's a flashback scene in the anime where Rena holds her arms open as Keiichi proceeds to bludgeon her. If Rena and Mion had enough physical prowess to hold Keiichi down to use the marker how was Keiichi able to knock out both girls with a baseball bat? At least one of them should've ran for their life. Keiichi was obviously screaming for his life, unless the syndrome makes the person act normally outside while they're snapping inside. How could they still go to his house to play a punishment game when things were so out of control, couldn't they see how terrified Keiichi was? They were psychologically abusing him during that last visit. Rena and Mion knew exactly what Keiichi was going trough since Satoshi behaved the same until he snapped.

It was obvious Keiichi was very afraid of them and didn't want to keep in touch. They saw Keiichi growing suspicious of them, and saw him training with a bat for self-defense. They wanted to forget the violent past and still act like nothing happened. How could Rena and Mion be so 'naive' in order to keep in touch with Keiichi? They were indeed hiding things from him.

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