Here is the full list of all 21 Jigoku Kisetsukan: Sense of the Seasons achievements.
Complete the game with Mizuiro
Complete a story at Normal difficulty
Complete the game with Tenshi
Complete a story at Easy difficulty
Complete the fourth level
Complete the third level
Complete the second level
Complete the first level
Start the Game
Complete the game with five characters
Complete the game with six characters
Complete the game with Eiko
Complete the game with Nibiiro
Complete the game with Fumin
Complete the story
Complete the game with ???
Complete a story at Hard difficulty
Complete a story at Hell difficulty
Complete a story without killing anyone
Complete a story without dying
Complete the game with ??? at Hell difficulty