First kill that bomb-launching stove, then the knife lancer, that monster that can shield himself with a barrier, the other who can teleport, and finally the guy with the shield, to open the door. And learn grammar. BTW: if you finish the game in less than an hour, regardless of the percentage of mana stones and
books collected, you get the S rank. A door near the start opens, you get the Fire++, so you can avoid some parts of the game, and destroy many bosses rapidly (the chameleon goes down with two big fireballs). By leaving behind some mana stones, you can finish the game in less than 30 minutes, getting the SS rank.
Another secret door opens and you get the Bat power from the start. This way, if you are good at using it, you can even avoid getting the Jump++. I finished the game in 13 minutes, but no more ranks, or pity.