This review contains spoilers, click expand to view.
This game gives me the different kind of chill. The decent art with the dark atmosphere, the deadly traps and monsters, and the music. The memory fragments are kind of tricky, which is worth to replay the game to collect all of them. Normal puzzle games make you go all kind of places to find things and read stuffs, but The Firefly Diary requires your skills, quick reaction and right timing which are something I like. Cute Mion is the reason I keep playing this despair game because I cannot allow to see her never be saved by my own hands (funny is in the artbook limited edition, the book says quite the same thing about Mion).
When you actually try to figure it out what the hell is wrong in this game, you try to find each memory fragment and the truth about Mion and the world she lives. When you collect everything, each chapter makes sense to you. Like the boss in chapter 2, the forest and Mion's corpses in chapter 3, the plants can kill shadow monsters, and the shadow parents. When I understand that, it makes me feel this game is better than I thought, NIS shapes the game perfectly.
To make the game less fearsome like trying to collect all memory fragments but you really hate to go through 100% the game, you can select chapter and specific area to find them. For example, I didn't know there was a fragment inside the box hanging in 1-3, so I go to select chapter 1 -> 1-3 to find it, then u can select other area like 2-2 to continue your searching without going through the whole nightmare (Also to skip sometime to unlock secret place).
The cons of this game are the controlling in either the touching screen or the joystick are really getting my nerve sometimes (especially when I have to guide Lumen out of her dead zone). Puzzles of this game is its strong and also weak point. Several places when you need to be extremely careful can kill you a dozen of time before you can proceed further. In fact, there's a high chance that you need to die before you can solve the puzzle.
Those reviewers who give the game bad scores is because they are impatient about the controlling system and the puzzle. You can't accuse a horse is bad because you can't ride on it when you don't have the skill and try to spend time to train. In my opinion, I feel they try to make the game look bad. Mion is slow because she is a young frail little girl in a dreadful place. When you actually finish the game, you can make sense why she's slow + fast pace is not what this game made of.
In my conclusion, it's a strange horror puzzle game that you, who are reading this review should try. For anyone who is emotional, you would try to finish the game 100% story, and the same for anyone who is like me, doesn't want to abandon Mion. This game has no text but you can figure out everything. One thing I want to say after I finish the game is "Screw the war".… Expand