Here is the premium version of the English translation by Kawahagitei, his first brand new original brother/sister story in a long while featuring brand new characters.
A little sister loves her brother so much, that she wishes to marry him when she grows up. The brother joked that by the time she grew up, she will forget all about it. She grew overnight inexplicably and when he sees her the next morning, he couldn't help himself and fucked her. The day after having sex, she has had another growth spurt, significantly taller and fully matured, ready to 'wrestle' again with him, setting up the sequel.
If you are acquainted with Kawahagitei's stories, you will know where this will go. Her belly will supposedly be bigger than anything he has ever made, so im excited about the sequel and so should you, if you like it.
In the sequels, the little sister will be even taller, according to Kawahagitei himself, which is scheduled for October.
You can also read the novelization, that a friend of his made in collaboration with him, talking from the sister's perspective. Give it a read: https://www.pixiv.net/novel/show.php?id=25169046