Putting 1 coal and 5 coals always result in a fail

1 Coal:

• Fail

2 Coals:

• "Hmm, I think I should lower the heat or it might hurt to smoke."
  
• "So... how much should I put in? I think the smoke was a bit strong, so maybe less."

3 Coals:

• "Right, I think it'd be good to maintain the current temperature without adding too much."
  
• "Okay, time to change the charcoal... The smoke feels okay, so I should keep it this way."
  
• "How many pieces should I add? I'm thinking a moderate amount."
  
• "Hmm... about the number of charcoal... I want to keep it the same."

4 Coals:

• "Hmm, the charcoal... Maybe I should add more to really get the flavor out."
  
• "The flavors were a little weak. Maybe some more charcoal will do the trick."
  
• "I should put more. I think it's okay to raise the temperature a bit."

5 Coals:

• Fail

Once you invite a girl certain number of times, game will prompt an "Important choice" to you. One choice initiates Happy ending and the other is Bad ending.

Once you've entered the Happy Ending option, you still need to invite her to the store the next day to reach the ending.

After entering any of the Happy Endings (i.e., picking either person's HE option), others will not appear the next day.

If you want to enter the Happy Ending with Amu, and Kokoro's option is triggered first, you have to choose Kokoro's Bad Ending option first before you can successfully trigger Amu's option.

• Close the store without entering any of the HE lines, and reach the ending: Closed.
  
  
• After entering a character's BE line, only that character's preferred ingredients, drinks, and fruits will appear in the recommendations for the next day to reach the ending: Abandoned
  
  
• After completing the HE for all three characters, go back to the main screen and click on "True Ending" to enter and reach the True Ending.

There are 35 types of hookahs in this game.

Each hookah is made by choosing three out of the five raw materials (fruits, desserts, beverages, spices, and nuts)

The type of beverage has nothing to do with the order of the materials.

Here's the list of all of them:

• 1. Fruit - Fruit - Fruit = Fruity Blend
  
• 2. Fruit - Fruit - Dessert = Applegum Blend
  
• 3. Fruit - Fruit - Spice = Summer's Arrival
  
• 4. Fruit - Fruit - Beverage Lychee Tea
  
• 5. Fruit - Fruit - Nut = Tropical Nuts
  
• 6. Fruit - Dessert - Dessert = Choco Banana
  
• 7. Fruit - Dessert - Spice = Jammy Cookies
  
• 8. Fruit - Dessert - Beverage = White Strawberry Latte
  
• 9. Fruit - Dessert - Nut = Apple Pie
  
• 10. Fruit - Spice - Spice = Cara-Mint Orange
  
• 11. Fruit - Spice - Beverage = Lychee Lemonade
  
• 12. Fruit - Spice - Nut = Extra Nut Coconut
  
• 13. Fruit - Beverage - Beverage = Lemon Cola Blend
  
• 14. Fruit - Beverage - Nut = Cocoa Orange
  
• 15. Fruit - Nut - Nut = Berry Nutty
  
• 16. Dessert - Dessert - Dessert = Devilishly 0 Calorie
  
• 17. Dessert - Dessert - Spice = Love Mint 13-1
  
• 18. Dessert - Dessert - Beverage = Halloween Blend
  
• 19. Dessert - Dessert - Nut = Valentine Blend
  
• 20. Dessert - Spice - Spice = Lemon Cake Deluxe
  
• 21. Dessert - Spice - Beverage = Caramel Macchiato
  
• 22. Dessert - Spice - Nut = Pistachio
  
• 23. Dessert - Beverage - Beverage = Spiced Muffin
  
• 24. Dessert - Beverage - Nut = Coffee and Cookies
  
• 25. Dessert - Nut - Nut = Caramelized Nuts
  
• 26. Spice - Spice - Spice = Fragrant Fantasia
  
• 27. Spice - Spice - Beverage = Jasmine Tea
  
• 28. Spice - Spice - Nut = Spiced Nuts
  
• 29. Spice - Spice - Beverage = Summer Party Blend
  
• 30. Spice - Beverage - Nut = Viennese Coffee
  
• 31. Spice - Nut - Nut = Rich Vanilla
  
• 32. Beverage - Beverage - Beverage = Royal Milk Tea
  
• 33. Beverage - Beverage - Nut = Matcha Cappuccino
  
• 34. Beverage - Nut - Nut = Almond Milk
  
• 35. Beverage - Nut - Nut = Triple Nuts

If you want to see how they all look like check out this guide here