Great work! I just downloaded the app and was testing it out. I like the way the onboarding is down with a gentle suggestion of what to do first without locking the user out of parts of the app. I believe users should be able to explore as much as they want to decide if something is beyond their current comprehension.

One thing, when learning some of the hiragana, the sensitivity seems to be set pretty high on the precision of handwriting to get accepted. I must have tried え 10 times before just swiping down to get out of it because it would not accept the second stroke. I didn't have trouble with the others leading up to it though.