On the episode 1, there are no keys. So, the secrets on this episode is only crystals. Crystals begin to appear on the level 1-5.
There are 2 crystals there. You won’t miss the first Crystal because you will move pass through it.
For the 2nd crystals, it’s below the cracking platform, exactly before the finish line.
There is only 1 crystal on this level. You will also see this crystal, but you can miss it if you glide to the wrong direction.
The first one, you can get it from the gift box that is located before the boss battle.
And for the last one, you can find after you have beaten the boss.