Motto! Haramase! Honoo no oppai isekai ero mahou gakuen!

The protagonist, Takumi Kazuya, is a contributing author to the
erotic light novel website [Let's do erotic novels!], where he writes erotic
fiction. Soon after, he was contacted by a light novel publisher and his work
reached a million hits. He sat back in his bathtub thinking of his erotic
novel and his road to fame. "How long are are you gonna be in there? Dumb
brother!", His younger sister yelled out to him as he was thinking of his
novel. Annoyed, his sister elevated the bath temperature to MAX and there was
an accidental explosion. He heard a voice across the white light. He soon fell
out of the white light to the other side. "Oooohhhhh!" Kazuya had arrived in a
different bath in a new location, surrounded by a bunch of surprised girls.
"Is this heaven?" Every one of these girls had gigantic boobs. It's like milk
was just ready to come bursting out of them. As soon as Kazuya thought that, a
magic square came forth and the girls' breasts started shooting milk all over.
Could he now use magic? Screams of surprise filled the room. In the women's
hot springs of a parallel world Kazuya was now reborn. This is just like in
the erotic light novel that he had written. He now realized his erotic desires
work as magic on girls!? It's time to conquer this other world with ero-magic!