Here is the full list of all 18 RUKIMIN's Disappointing Adventure! achievements.
Game over on the title screen.
Game over on the game select scene.
Overflowing from the screen.
Died once.
Died 10 times
Died 50 times
Died 100 times
Clear with less than 5 deaths
Eat rice balls
Beat Mr. Bomber.
Beat SUZUKO.
Found white asparagus.
Returned to the starting point.
Completed faster than 10 minutes.
Finished the tutorial.
Completed the mission.
Meet a macho hero.
Escaped from the wall.