Here is the full list of all 17 Umihara Kawase Shun Steam Edition achievements.
Finish Stage 0 within 15 seconds
Finish "UmiharaKawase Shun"
Finish "UmiharaKawase Shun" without losing a life
Visit all stages
Finish all doors
Obtain all backpacks
Catch all enemies
Finish Stage 0 within 10 seconds
Use door that returns to Stage 0
Catch Sharksucker thrown by Shark while in air
Catch 3 Flying Fish that jumps from the bucket
Catch all Kid Frogs during Tadpole battle
Catch all Squids during Squid battle
Finish Pufferfish battle with only blowing it away twice
Let 3 birds land on body at the same time
Travel upwards 2 screens or more without touching the floor
Make a catch after moving more than 2 screens with lure attached to the enemy