The easiest way to reach the first stage of Future World is to take the warp in the first stage of Feudal Japan. It is located behind the second barrier wall (from which you receive a hidden 1-up doll). Destroy the wall and push up at the cave entrance to warp.
If you have returned here from after defeating the Super Computer in the fifth stage, the stage is a little longer and you must pass through a different beginning. Look for a warp to the Prehistoric Times very early on when you find yourself back among the usual start to the stage. After you cross the very first bridge, you will notice a treasure chest below in the water flow. This chest can be very difficult to reach but it is possible if you fall through the gap in the bridge and carefully place a set of gargoyles blocks beneath you back to the left. Eventually, you will reach the chest which contains a nice reward: a 1-up doll. Whether you get the chest or not, proceed to the right over the rest of the bridge, watching out for the bouncing insects. After the bridge, there are a series of chests trapped in the rocks to the right. You can break them out by shooting the rocks. The first one has an Onigiri. Make sure you destroy the lowest set of blocks before proceeding to the low platform occupied by a number of Amoebas. Climb up to the higher platform, break the blocks above that and jump over the gap. While you can dig down into the middle layer of the next portion, it is actually safer to simply run along the top of the screen. When you reach a small shallow pool, you'll have to climb up and knock out the highest blocks to continue. Another valuable Onigiri is hidden in the low block just before the long waterfall. Just beyond that, a series of twisting Moais should begin to appear.
Boss: There is no actual boss for this stage per se, but a large number of Moais will appear on the right side of the screen and crash through the blocks as they travel to the left. Each one will leave behind a tunnel, and eventually you will be able to proceed closer to the card on the right. You can speed up the process by making your own tunnels. Once you collect the card you will be off to the next stage.
Once you arrive on this stage, your best strategy is to keep moving as quickly to the right as you can. You will be attacked by insects and a series of falling meteorites. There aren't a lot of treasure chests to help you, and those that are present will only slow you down. That makes it all the more important to find hidden treasures like the Onigiri in the second step of the staircase of blocks that lead you to the top of the screen One the other side, you'll have to begin shooting down some of the bricks to gain access to the pathway beyond. An invincibility feather is hidden in one of the bricks. You must continue to shoot through that layer. If you happen to run ahead and think that you've become stuck, you can break through the blocks that you stand on by squatting and jumping three times. Two tiers of platforms will appear. The lower one can be shot and destroyed, revealing a few hidden items. Meteorites will begin to appear again. Another set of platforms can be jumped over, or shot through and run below. After you encounter three chests in a row (the last one contains Onigiri), larger meteors will begin to fall out of the sky.
Boss: Like the previous stage, there is no actual boss, but an obstacle you must avoid while trying to make your way to the card at the end. In this case, it is a series of falling Meteors which plummet to the ground and crash through the blocks below, creating gaps which Gaou must jump over in order to survive. Once the card is in view, don't hesitate; begin building a staircase to the card immediately. If Meteors fall over the gargoyle blocks, they will be destroyed. Patiently replace them and continue on your way to the card.
Pass below the first platform, and prepare to shoot out some of the blocks of the next platform in order to get a better foothold, but watch out for the bouncing Kruuk aliens. You will have to advance through a series of platforms and avoid the Mecha Pill bugs that occupy them, until you find three chests next to one another. Meteorites will fall from the sky again. Advance to the fenced in area. Take the low path below the next platform to avoid the Amoebas. Eventually, you will see Mecha Bees bouncing in a closed off area. The wall that separates you from them can be shot and destroyed, revealing an Onigiri inside. You can take either path. If you take the low path, you will have to push the block at the end out of the way to continue. Next, you will encounter three pairs of cylinders. If you try to jump between them, you will most likely get caught in there with a set of Kruuks. Sometimes Amoebas roam back and forth on top of them. A treasure chest usually lies on the second cylinder, but it can be hard to reach if the space between them is not safe. Beyond those pairs, you will have to climb over very high cylinders, one of which contains a chest with Onigiri. As you move on, Missiles will begin to appear from the floor and fire forward when they reach your vertical height. Then you will find three more chests, one with another Onigiri. After that, you will reach the boss.
Boss: The Byebull is an alien that behaves very much like the Mural boss at the end of the seventh stage in Feudal Japan. It remains stationary in the upper right corner of the screen while shooting smaller aliens at Gaou. If you build a set of gargoyle blocks along the right wall, you can get close enough to it to fire quite rapidly at it from below, destroying it quickly and collecting the card. Another alien will fall to the ground in an egg and hatch, but you needn't worry about it if you are up on blocks.
This futuristic city stage starts with a secret passage below the first platform, including some hidden items, followed by a series of platform jumps while the Evil Spirit faces float across the screen. An Onigiri is in a chest lying on a low platform. You must fall and stop yourself with a gargoyle block in order to collect it. Below the three statues of women pouring water, there is a secret pathway which you can break open by squatting and jumping on. Breaking the blocks will reveal different items once you shoot them. Watch out for the Amoebas that occupy the tops of the high platforms. After a high platform with a time stop necklace in the chest, there is a building on a mid-level platform that has a hidden chest in the ground below, containing an Onigiri. Chest will fall out of the sky until you reach a set of steps, the lower of which can be broken and shot through, revealing a mirror that lets you pass through the ground. When you reach another split, the block that lie in front of the high platform can be broken, and also hide an Onigiri. The low chest before a wall of blocks only contains a point bag.
Boss: The wall itself actually represents the end of the stage, where you must shoot through a series of blocks in order to reach the card in the upper right hand corner. Hidden in the blocks are a couple of spherical enemies which follow the contour of the space you create by blasting out the blocks. They should pose a minimal threat, and you should be able to collect the card in very little time.
Start by running beyond the three chests and turning around to open them. The first one has an Onigiri. Watch out for the Quasail aliens that run about, and the meteorites that fall after them as you proceed to the right. Jump to the high platform, and watch out for the Mecha Bees as you jump over the staircase of blocks. A hole can be punched in two locations of the wall that follows, high or low. The low routes leads to chests while the upper route is crowded with Amoebas. Meteorites will begin falling again, so be sure to collect the Onigiri in the chest that follows. Navigate over the next series of platforms, ignoring the low lying treasure chest (point bag). Just before the boss, there is a high platform with a chest that contains an Onigiri.
Boss: The Super Computer is another very stationary and easy boss to defeat. It sends out football shaped objects that bounce around the room, but don't necessarily pose a significant threat to you. Create a gargoyle platform off the ground so that you can get closer to the core and fire at it more rapidly. Eventually the core will be destroyed and you will reveal a Konami symbol behind it as you collect the card.
Note: At this point, you will be returned to the first stage in the Future World.