Magical Explorer, Vol. 1 (manga)

Reincarnated as a character in the legendary erotic game, "Magical
Explorer," it doesn't
take long for our hero to discover that
he's been designated the unlucky side-character
rather than the
game's lady-killer protagonist. Not to worry, though! Armed with
his
vast knowledge of the game (and a few cheats) he'll do whatever it
takes to win the
hearts of the game's heroines and emerge as the most
accomplished student at the
Sorcerer's Academy!