- Anticlimax Boss: Murasame himself, who can easily be defeated in just a few seconds by wailing on him with fireballs as soon as he opens his mouth. He takes only five hits.
- Demonic Spiders: Spear Samurai and Flame Ninjas, which are very difficult to beat with anything less than triple fireballs.
- The Porter rooms, which contain the staircases you need to climb in each castle. Every one of these rooms is a mess of projectiles that are almost impossible to pass without taking damage—that is, unless you've saved a Lightning powerup, which will instantly kill all of the Porters and make the staircase appear immediately.
- Game-Breaker: The "King" powerup, which lets the player shoot out three projectiles straight ahead at once. When combined with the fireball powerup, it is hands-down the most effective weapon in the game.
- Power-Up Letdown: The windmill sword powerup. Its low power and slow rate of fire compared to fireballs makes it little more than an obstacle to avoid, as accidentally picking it up will likely lead to your death.
- That One Level: The fourth castle is the hardest level in the game, due to its lack of easily-accessible health refills and abundance of Flame Ninjas.
YMMV / The Mysterious Murasame Castle