you gotta raise your charm like alot then just keep on trying to sit beside her in her class. then it will trigger an event where you help her. then the secret ending is that just make sure to follow the choices in the guide. if you already got elani good ending then.
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when siri pin you down when your with elani (his annoyed at you in here btw xD) anyways say that you now him and then you unlock the secret end ^.^
Ps. you gotta unlock the good end before proceeding to get the secret end.