Let's Fall in Love the Ero-Manga Vol. 2 エロマンガみたいな恋をしよう

Azusa and hiro are siblings. Azuza's libido once a month becomes bottomless. And then that day has come again, thus, Hiro must dedicate all his attention and efforts that day to satiate her sister Azusa's sexual desires ... will he has the energy needed for such huge task? Hiro can only wonder when this apparently "heaven" will end, his mother advice him that she was the same as Azusa when she was younger and the "cure" was having a baby...