Despite the fact it was already explained here on another page, i'm gonna tell it anyways.
so there are 3 endings, the rape ending, the yuri/Futa ending, and the love ending.
rape end: just fuck the girls each time you have a chance and use 'em like a cum-dumpster, as in, beat them and cum as fast as possible. unlocks extra level 1 (or infinite mode as i call it, fight the girls for as long you desire, dialogue is changed to reflect the rape ending)
yuri/futa end: you MUST learn the ability to temporally turn the girls into futas, put one girl in a difficult situation (knocked out, bound by your magic psy-energy, or turned horny by hypnosis) and quickly give the other girl a dick, also make sure both of them get to be the futa at least once. and
DO NOT fuck them yourself.
Love end: similar to rape ending. but instead of just a quick fuck'n'cum, you have to fuck them both until they start to enjoy it (which means, their dialouge has hearts in it and all that) dunno if dialogue choice matters. basically, premise for this ending boils down to "fuck the lesbians so good and hard that they turn bisexual". also this ending unlock extra level 2 (infinite battle, but this time the dialouge reflects the love ending, and this time, the girls actually enjoy the sex)