100% Route
Note: this page was adapted from swordsmankirby's guide. Some strats may be outdated.
5-1
The version I'm presenting here (for now) is actually the double fire route for 5-1 and 5-2. I strongly recommend double fire for 5-1 and 5-2, because single fire is only a little bit faster while being significantly more difficult.
Combine for double fire using the two Bobos and follow the route to the end of the room.
In the second room, don't use double fire up the slope. Because of the long recovery animation, it turns out to be faster if you just run to the ladders. When climbing up the ladders, jump off the top of each of them onto the next one by either grabbing the ladder's ledge or doing a small jump when you're near the top of the ladder. When triggering the Waddle Dee cutscene, also don't use double fire here. Like the minecart autoscroller, jump repeatedly to save time. Shard 1 is on top of an igloo after a few food items.
The Chilly miniboss becomes invulnerable when attacking, and even with double fire, you won't make it there in time before it attacks. In the meantime, break the ice stalactite with double fire before doing two double fires to kill the miniboss. If done correctly (i.e. three hits per double fire), the second double fire will end before the door opens, allowing you to float up to collect Shard 2. If that's too risky, instead of doing a double fire to the right, you could also do three double fires to the left (reminiscent of the single-fire strat). Since the miniboss's attack doesn't last that long, one small timesaver is to use the tail end of the double fire to break the ice so you don't have to float as high up or fall as far down.
In the following room, fire across to the second hole in the ice (past the third pillar) and drop in. The pillars are all evenly spaced, so the same double fire setup will work. In the water, swim to the right and double fire through the hole. Collect Shard 3 in the alcove in the bottom right and go back the way you came. To line up the double fire to the left, use the height of the rightmost enemy.
Double fire to the end with the route, but note that it's pretty precise. There are alternative routes that involve floating up close to the top of the screen, but these are significantly slower. The jump between the floating platforms in the second clip can be done more safely with a puff, and jumping to the next platform makes it easier to clear the Putt's boulder.
5-2
In the first room, run forward and jump into a double fire so that the recovery happens when you're over the pit. Follow the double fire route and drop down for Shard 1. Note that the first double fire in the second room should be as early as possible, so just mash when you first start the room. I suppose that instead of puffing, you could double-fire into the shard, but that's pretty risky because the camera angle there is bad.
Shard 2 is located in the top-left of this Zebon room. Note that the Zebon is spinning clockwise and "rounds up": if you press A in between, e.g., west and northwest (right), it'll stop at northwest. This also means that it's not possible to immediately shoot upwards.
Follow the double fire route until you reach the Ticks. Swallow one and continue onwards. For the set of blocks with the Mopoos and Cairns, you can use needle (middle) or jump on top (right), though the latter is more precise and depends on the Mopoos' cycles.
In the room with the pink clouds, most enemies can be headbutted or simply jumped over, but the Maws require you to manipulate its jump height by running into the slope a little bit before jumping.
Towards the end of the room, combine for lightning rod with the Sparky. The Sparky can jump off into the pit, as shown in the bottom-left, so the best way of respawning it is to go to the right, kill the Maw, and walk back to the left. In my experience, using the needle at the peak of your jump right above the Maw is the most consistent way of hitting it. If the Sparky tries jumping off again, you can intercept it since you're now standing closer to the hole. As with the other Sparky combination in 2-1, missing the throw wastes a lot of time, so be very careful.
The end of the level has a Maw on the ceiling, which can be bypassed by jumping near it, and a set of four Mopoos. Since their cycles can be a bit strange sometimes, I like to jump preemptively for the ones that spawn from below.
The miniboss is pretty random, but if you stand at the bottom below the barrier, you should be in a good position most of the time. Sometimes, the lightning rod can get off two hits because the Mopoo has few invincibility frames. After the fight, grab Shard 3 and slide out. The reason for keeping the powerup will be seen in 5-3.
5-3
The "shopping mall" level used to be done with fire of some sort, but it's not only slower by a few seconds, but also harder.
Ideally, you still have the lightning rod from the previous level. As you pass through the first loading zone, put the powerup in your mouth, and in the next room, spit it out on the two Poppy Bros. If you don't have a powerup, it's fastest to just spit one into the other. On the next conveyer belt, headbutt the second Bouncy. To get around the Putt's boulder on the one after, there are two main strats: one where you puff the Putt and jump up the platforms, and one where you float past it. I believe the former is slightly faster. After grabbing Shard 1, jump a little before the ledge so you land straight on the conveyer belt. Jump past the other Putt with a little float and puff and take the elevator.
On the first floor of the next room, there are three Mahalls and two Sawyers. Either you can form a double-star and kill all the Mahalls at once, or dodge all of the enemies carefully. I think the double-star strat is faster because you're able to slide three times. A really simple way of forming the star, as shown in the middle, is to stand underneath the first Mahall and start inhaling, but this animation takes a long time.
The second floor consists of three Gloms and two Fishbones. Here, three strats are shown for getting around these enemies. I find the first strat to be most consistent: grinding against the wall while jumping allows you to just hold left the entire time. However, the third strat allows you to get some food if you're low on health.
In the first strat, get one of the Ticks and use the needle powerup to get past the I³ enemies. For a tiny framesaver, you can try puffing a Tick instead of sliding into it, but the timing is really tight. The second I³ can be slowly jumped over (with the help of a puff), so you don't have to take extra damage there. A simpler strat is to inhale the second Tick and swallow it while waiting for the first I³ is falling. The rest of the floor proceeds the same way as the previous strat.
The miniboss is a straightforward fight where only three attacks are needed—each use of needle can hit twice. Grab Shard 2 after the fight. The Bo enemy on the right can move randomly in your way, so you might jump into the shard while using needle. In the next room, press the switches corresponding to the colors of the fruit Adeleine draws. The fruits are, in the order of the switches in the next room, cherry, peach, nut(?), melon, grape, lemon, orange. I like to do a needle into the wall to get in position to slide, and I start the slide as Adeleine draws the third fruit. Shard 3 spawns in the middle above the green switch, and depending on which switches you pressed, you might be able to slide off of one of them to get to the door quicker.
In the first section, you can just run underneath everyone, but you can save a bit of time by sliding off the platforms. The first slide is not really worth it since you have to puff into the Kiyobi's spear, but I think the second slide is definitely worth going for. Afterwards, in the room with the falling bookcases, take out needle and run into the Cairn to get drill. As with 3-3, jump out of the water repeatedly in the fishtank. I like to use drill as I jump out of the water to get a small boost and take care of the first Sawyer in the next room. Use drill as shown in the bottom-right to take out some inconvenient enemies.
The Shotzos in the last room will try to predict where you go. As long as you route out your jumps, you shouldn't ever get hit.
5-4
Usually when you enter the hole, there will be a brief cutscene where Kirby climbs down a ladder. Having a powerup above your head or in your mouth will cause Kirby to start falling immediately (left). It's possible to get past the Sawyer at the bottom, but it's pretty precise. Drill can be shot downward, breaking all the blocks at once. Throw away the powerup, get fire, and navigate to Shard 1. For both powerup swallows, you can do it while falling off a ledge to save a bit of time.
In the Dedede section, the primary concern is those crushing hammer machines. There are six in total, and ideally you alternate between waiting for them to fall and getting in front of the cycle. It's possible to get four early cycles, but it's really risky and not worth it. The whole time, there is a conveyor belt running to the left, so it's best to jump as much as possible. As shown in the clips, the best places to jump are enemies and "doorways." For the third clip, it's much better to jump over the Turbites than to hammer them. Finally, there is a Sawyer at the very end that's possible to jump over.
In this room, there are conveyer belts going both directions. It's faster to use fire on the red conveyer belts moving to the left. For the first I³ I like to use fire to get past it without taking damage. My visual cue is to fire right at the enemy's shadow. If done quickly enough, the fire should be a short one so that it ends around the time the I³ hits you. You can also get behind the I³ with a slide (middle), but you'll always take damage and it's more precise from my experience. At this point, remove fire and grab the cutter enemy. Unlike many of the previous combinations, Cutter is swallowed so that you can make use of headbutting. Finally, combine with the turbite on the ceiling. Note the small green conveyer belt optimizations in this section.
The miniboss fight can be a little finicky at times. As you enter, jump and start using the powerup, breaking the cage up top. As you fall, hit the Burnis either by turning around or swinging your lightsaber. The latter is more consistent, though slower because the animation is still going by the time you land. Jump and turn around to hit the Burnis three more times, and then take out your powerup and throw it for the remaining two hits. When the powerup is active, it takes a while to remove, so press down to put away the lightsaber. Afterwards, get fire from one of the Magoos that spawn, grab Shard 2, and leave. If the Magoo on the left just dropped into the lava as you threw the powerup, go get the one on the right since it'll spawn sooner.
The following room has five crushing platforms. Essentially, the only one you can get a quick cycle on is the fourth one, which involves using fire to get through the third one quicker. This saves about 8sec over the slower cycle, plus the pattern of the Shotzos in the background is nicer.
In the final room, you want to combine for fire sword using the fire powerup you already have. There are three cutter enemies, so keep fire until you reach the third one (left). After maneuvering around enemies, grab Shard 3 on the floor with the Scarfies. Afterwards, jump up and beat the crushing electric platforms. When jumping up to that floor, jump into the middle of the "grate" to avoid the bubble the Mahall shoots out. The slide off the ledge is crucial for getting past the platform. Afterwards, the Zoos enemies will try to throw sparks at you, but these can be headbutted out of the way.
If you die in one of the last two rooms, the best backup for HR would be to get lightsaber. There are a couple of spark enemies, which you can combine in the same way on the Fishbone.