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