I was able to get my hands on a WIP machine-translated copy of the original Slime Mori-Mori thanks to Nick, check out his work!
This is honestly a very solid foundation for the Dragon Quest Heroes spinoff series. You play as the iconic blue slime, living out their quiet rural life amongst other friendly slimes when suddenly, the Plob show up and kidnap everyone from your village and it's up to you, the hapless and adorable squishy hero, to rescue everyone and repair your village while beating the Plob at their own game of discovering the world's many secrets. If you've played the DS sequel to this (Rocket Slime), then this basically controls the same; you can stretch out your slime's body and let go to perform an Elasto Blast, which propels you into enemies, obstacles, and other objects and will often shoot them into the air, where you can then catch, carry, and throw these objects and enemies to your delight. The Elasto Blast is both your main form of attack as well as a movement and object interaction tool in this sense.
The original Japan exclusive Slime Mori Mori focuses on dungeon traversal; your Slime buddies have all been boxed up within the various ecosystems scattered across the giant island, and it's your duty to break open these boxes and send them home by either carrying them back to the entrance, or throwing them onto balloon lifts and train cars headed back. The backbone is solid enough strictly speaking, but as someone coming from many hours spent in Rocket Slime, this is where the lack of quality of life starts to show a bit. All of the balloon lifts and many of the train cars/cargo floats have a capacity of one, which means you can only chuck one passenger/object/monster on at a time and have to wait around a little for the next transport to come about. In the case of balloon lifts, this wait is exacerbated since it respawns off screen and you have to meander about in a separate area of the dungeon before it comes back. Dungeon exploration in general has some great ideas, but again, when comparing to its successors, becomes a bit rote. A lot of the exploration boils down to carrying over Bomb Rocks from other rooms to blow up barriers, or collecting an assortment of other objects elsewhere and bringing them over to statues to imitate their object order and unlock doors. The actual puzzle combinations outside of these two interactions are quite interesting though; there's a lava area where you have to drop loose tiles from an above floor to create platforms for traversal, there's a beach area with water spouts and sand where you can bury yourself to flip enemies and travel under tunnels, and so on so forth. It does suck a little that some progress isn't saved, such as the poppable Plob balloons that block progress in the mountain zone, but this is generally a trifle once you figure out the dungeon layout as is.
The real breadwinner of the original game however, has to be the over-the-top boss fights. Some of my favorites here include a fight against two twin Plobs (one with a fire gauntlet and the other with an ice sword) who attempt to take you down simultaneously but are susceptible to team damage (so it's more fun dodging their attacks and watching them actively interfere with one another), and a turtle monster who, upon realizing that you're using the sand to flip and damage it, floods the room with water to prevent burying and forces an old rival of yours to appear to help you out with fireballs and aerial dodging, transforming the fight into almost a pseudo shmup. Some of the fights do phone it in a bit (i.e. the 2nd golem fight in the secret forest is more or less a juiced up version of the 1st golem fight with slightly tougher attacks), but in general, these boss fights are exemplary of the cartoony and vibrant charm of the series. They're absolutely ridiculous and don't try to take themselves seriously whatsoever, and are a great diversion from the often repetitive dungeon crawling.
Again, my main reservation here is less that the game sucks, and more that it's just quite overshadowed at this point by its successors. I don't find the dungeon exploration very externally rewarding unfortunately; you can send some monsters and materials back to help repair the town or sell materials for money, but outside of some permanent health bar capacity/wallet upgrades and a few unlockable minigames, there's not a huge incentive to keep grinding out materials unless you really do care that much about fixing up your town as a good citizen. Dungeon exploration is also held back a bit by the arbitrary time limit (which will end your run if you're there past nightfall), so it does become necessary to keep an eye out on the day-night cycle gauge if you don't want to spend another 100G buying time sand as a fail safe. Having said that, the tank/ship battles in the later installments are a welcome improvement in tying all the different adventure game elements together, and definitely add more meat to the bone on what is already a pretty promising beginning to the series. It doesn't take too long to run through the whole game (maybe about 10 hours or so for my first playthrough), and while I admit that I can't comment too heavily on the dialogue due to the limits of the machine translation, the classic happy-go-lucky appeal of Rocket Slime is all still there with surprisingly well animated and colorful visuals. If you're a fan of Rocket Slime looking for more content, then I'd recommend giving this a shot just to check out its humble beginnings, and definitely don't be afraid to ask for help if you get stymied by the translated hints.
This is honestly a very solid foundation for the Dragon Quest Heroes spinoff series. You play as the iconic blue slime, living out their quiet rural life amongst other friendly slimes when suddenly, the Plob show up and kidnap everyone from your village and it's up to you, the hapless and adorable squishy hero, to rescue everyone and repair your village while beating the Plob at their own game of discovering the world's many secrets. If you've played the DS sequel to this (Rocket Slime), then this basically controls the same; you can stretch out your slime's body and let go to perform an Elasto Blast, which propels you into enemies, obstacles, and other objects and will often shoot them into the air, where you can then catch, carry, and throw these objects and enemies to your delight. The Elasto Blast is both your main form of attack as well as a movement and object interaction tool in this sense.
The original Japan exclusive Slime Mori Mori focuses on dungeon traversal; your Slime buddies have all been boxed up within the various ecosystems scattered across the giant island, and it's your duty to break open these boxes and send them home by either carrying them back to the entrance, or throwing them onto balloon lifts and train cars headed back. The backbone is solid enough strictly speaking, but as someone coming from many hours spent in Rocket Slime, this is where the lack of quality of life starts to show a bit. All of the balloon lifts and many of the train cars/cargo floats have a capacity of one, which means you can only chuck one passenger/object/monster on at a time and have to wait around a little for the next transport to come about. In the case of balloon lifts, this wait is exacerbated since it respawns off screen and you have to meander about in a separate area of the dungeon before it comes back. Dungeon exploration in general has some great ideas, but again, when comparing to its successors, becomes a bit rote. A lot of the exploration boils down to carrying over Bomb Rocks from other rooms to blow up barriers, or collecting an assortment of other objects elsewhere and bringing them over to statues to imitate their object order and unlock doors. The actual puzzle combinations outside of these two interactions are quite interesting though; there's a lava area where you have to drop loose tiles from an above floor to create platforms for traversal, there's a beach area with water spouts and sand where you can bury yourself to flip enemies and travel under tunnels, and so on so forth. It does suck a little that some progress isn't saved, such as the poppable Plob balloons that block progress in the mountain zone, but this is generally a trifle once you figure out the dungeon layout as is.
The real breadwinner of the original game however, has to be the over-the-top boss fights. Some of my favorites here include a fight against two twin Plobs (one with a fire gauntlet and the other with an ice sword) who attempt to take you down simultaneously but are susceptible to team damage (so it's more fun dodging their attacks and watching them actively interfere with one another), and a turtle monster who, upon realizing that you're using the sand to flip and damage it, floods the room with water to prevent burying and forces an old rival of yours to appear to help you out with fireballs and aerial dodging, transforming the fight into almost a pseudo shmup. Some of the fights do phone it in a bit (i.e. the 2nd golem fight in the secret forest is more or less a juiced up version of the 1st golem fight with slightly tougher attacks), but in general, these boss fights are exemplary of the cartoony and vibrant charm of the series. They're absolutely ridiculous and don't try to take themselves seriously whatsoever, and are a great diversion from the often repetitive dungeon crawling.
Again, my main reservation here is less that the game sucks, and more that it's just quite overshadowed at this point by its successors. I don't find the dungeon exploration very externally rewarding unfortunately; you can send some monsters and materials back to help repair the town or sell materials for money, but outside of some permanent health bar capacity/wallet upgrades and a few unlockable minigames, there's not a huge incentive to keep grinding out materials unless you really do care that much about fixing up your town as a good citizen. Dungeon exploration is also held back a bit by the arbitrary time limit (which will end your run if you're there past nightfall), so it does become necessary to keep an eye out on the day-night cycle gauge if you don't want to spend another 100G buying time sand as a fail safe. Having said that, the tank/ship battles in the later installments are a welcome improvement in tying all the different adventure game elements together, and definitely add more meat to the bone on what is already a pretty promising beginning to the series. It doesn't take too long to run through the whole game (maybe about 10 hours or so for my first playthrough), and while I admit that I can't comment too heavily on the dialogue due to the limits of the machine translation, the classic happy-go-lucky appeal of Rocket Slime is all still there with surprisingly well animated and colorful visuals. If you're a fan of Rocket Slime looking for more content, then I'd recommend giving this a shot just to check out its humble beginnings, and definitely don't be afraid to ask for help if you get stymied by the translated hints.