I thought it said true end, no? and is there really a way to complete without having any sex? The teacher, red manto, and the big sis, I don't think it is inevitable.
Nekotama youkai can see her (she mentioned "If my voice get loud, the golden haired girl will notice"), but she is a youkai anyway.
As for the 4 crystal, I think 1st is the Erika in the purple mirror world scene, 2nd is bad end, 3rd is true end, 4th is Hanako in the old school building scene.
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