I can't remember all the mainstory one's but the are 4 missable one's in the exploration zone ( feline hunting grounds ) with the red encounter orbs .
There no are H-Scenes for Yoshi if thats what you want to know, and there not gonna be any before 0.7 (it's more likely going to be 0.8 or 0.9, somewhere near the end of mainstory )
Here are the exploration one's anyway
1. Yoshi teases you and playes a game with you. You get a talisman with +2 for almost all stats as a reward.
2. Yoshi teases you and almost lets you have your way with, only to disappear last second. Another Kitsune Appears and gives you the initiate's robe (+25% exp/ skill : firepuff)
3. Yoshi appears and gives you a back message.
4. Yoshi offers you to be her apprentice if you accept she will upgrade your skill firepuff to fireblast . If you decline she will be sad.