Awe man, hope there are more bodyswap in the near update!!! Is it really The End, because I don't see the conclusion anywhere except she is going to get raped!!!
Both girls hit heads and swap of course. Shuuichi doesn't believe them at first, until the one girl as Makoto kisses him, and his real GF that Makoto is swapped as ends up super timid in the kiss, so then he believes them. She then forces Makoto to have sex with her BF in her body saying why does it matter since it's her body anyways. Which orgasm causes them to switch back. Makoto is then taken to the edge of climax and Shuuichi stops, which leads into Ch2.
Makoto is then at home and can't stop masturbating, feeling unfulfilled and wondering if it was some sort of hypnosis. After school the next day she is coerced into following them home to talk. Of course this leads to the predictable outcome. Shuuichi then tells her he's swapped with the other girl before. They don't know how it works exactly, but when it works it happens via kissing. Just after he puts it in Makoto, the other girl comes back and comments on how Shuuichi is big so it must really hurt and says they can switch then to relieve the pain for her. Then you have it leading up to both girls kissing to swap back and forth rapidly leading up to orgasm.
Rest is apparently story padding for page-count, and just includes another classmate of hers saying he had the okay from Shuuichi to do it with her and they end up swapping once as well.