I went back and managed to get to the end! What a cute ending! Also I feel really dumb since the solution was kinda obvious! I think my feedback is kinda invalid now bahaha. Thanks for the tip!
Spoilers below for last two notes of the game: (For others who might be reading this lol)
For the second to last note, I believe you have to NOT brew a second cup of tea for the adventurer, then serve Horns his favorite drink. For the last note, you have to put 3 tangy berries and serve that to the adventurer when you offer a second drink to him.