Magical Explorer, Vol. 2 (light novel): Reborn as a Side Character in a Fantasy Dating Sim

At long last, Kousuke enters the main setting of the erotic dating sim he's been reincarnated into, Tsukuyomi Magic Academy. But between using his knowledge of Magical Explorer to win the hearts of all the heroines he can and his relentless pursuit of strength in the depths of the game's hidden dungeons, Kousuke's student life turns out to be anything but easygoing. And that's all before a heroine shows up and claims it's her duty to serve him!