Thank you for playing my little game to the end, and I'm happy you enjoyed it so much!
Yes the lack of healing was very much intended, so I'm glad you realized it. A few people were really bothered by having to use items to heal, probably because we're all used to just having healers in RPGs (and honestly, when I have one in my party, whenever I rely on items it feels like I'm playing the game wrong somehow xD). Giving Shida and Cindy healing was also supposed to remind the player of how disfunctional their party is, and especially with Shida I wanted to make it feel like the party was finally complete. (Fun fact, Cindy was actually supposed to join the party in an earlier draft of the story, but I figured being a merchant would be more interesting.)
I made it so you can only find the diary parts in order, and the 3rd and 4th parts are only available after the credits. So if you want to try tracking them down I'd suggest you try retracing your steps throughout your journey again. I made the secret side quest just for the completionist psychos like me tho, so don't feel pressure to do it xD
And the next game will be a sequel. It will take place soon after Huyuchi village's second quest.