This is the sword that appears before Yuko on her way to school, and thus the sword you begin the game with. Although powerful in its own right, it is the weakest sword that Yuko will wield. It fires a single projectile straight ahead, enough to damage enemies that are hovering enemies in front of Yuko, but not those crawling on the ground.
High Beam Sword
Shortly after you enter the ruins of the dream world, you may find a house with a man inside who recognizes your need for a greater weapon. He will swap your old sword for his improved sword. It fires two projectiles in parallel at a slightly longer distance, boosting Yuko's ability to fight at a distance.
Wide Beam Sword
This sword can be obtained in the jungle. It has a considerably wide range of attack, sending three projectiles out in an expanding fashion. However, because the projectiles fan out, it can be difficult to use against enemies who are directly in front of Yuko. Use it carefully.
Laser Sword
A blacksmith in the ice world can convert the wide beam sword in to the laser sword, concentrating it's three projectiles into one focused wave. It's offensive power is pretty considerable, capable of defeating most minor enemies in one hit. But it is still not the strongest sword in the game.
Valis Sword
The Valis Sword is the only sword that has the ability to defeat Rogles. It is found in the ice world, although it is necessary to defeat a boss in the underground first to obtain it. Despite the difficulty in collecting it, it's worth the effort for the increased power.