I am basically a non-gamer, so you may want to take my feedback with a grain of salt… :D
I think the story is interesting. It reminds me of a manga called "Delicious in Dungeon," in which the heroes run out of money and food on a mission and decide to slay and eat the monsters along the way. So, I was excited to see a similar story in a game.
I was excited to see a tutorial as I am a total noob for this genre of games. I really appreciate the details to learn more about this type of gameplay, but it feels like a lot of information to swallow in one big bite. I feel it would be best to space out the information and build up gradually. For example, you may first start with the very basics to pass an easy baby-step first round with just two slimes (better yet, just one) as the initial journey. Then, the second round comes with a new challenge that needs new knowledge. You provide the relevant instructions at that point.
Introduce the 3rd and 4th slimes in the later round when the challenge calls for extra members in the team, and so you introduce the new and relevant tutorial information at that point. Maybe the slimes find the others from the previous party, so they join forces and combine loots; or some newcomers decide to come catch up with you. This will also give you a team with unique individual experience or skill levels, basically right off the bat.
In the dialog, it would be nice to add icons/graphics. For example, add the slime color image next to the name, for example, Helen. So, I can quickly identify which one is Helen by the color icon shown in the dialog. A sprinkle of graphics in the dialog helps break up long sentences and helps players pick up key points more quickly.
I played maybe 3 or 4 battles, and felt I want to experience something else in-between at least to replenish the health and take a break from the battles.
And visual and sound effects… You may already have them in your plan. Use visual and sound effects to spice up the attack/defend. Give each type of action a different visual and sound effect to make them more memorable.
About the weapons collected, maybe I overlooked the information in the tutorial… but what do I do with them? Can they be converted to health? When and how do the slimes eat them? Battle after battle, I see the slimes' health decrease but don't see how the loot gives them any instant gratification in return.
I can feel you are excited about your project and have been working hard on it. I look forward to seeing the improved version in the future!