In order to unlock this achievement, you need to collect all of the optional entries for the Trivia section of the Notebook. There are 5 in total, all of which can be found during the optional investigation in chapter 1:

Entrance Area:

• Examine the little doll in the bottom right of the screen.
  
• Examine the masks hanging on the wall.
  
• Examine the sign above the alcove with the hanging scroll.

Dining Area:

• Examine the one-eyed umbrella on the very left of the center table.
  
• Examine the zombie cat in the bottom right.

In the Character Profiles section, an additional [Ex] page can be unlocked for each of the 10 main characters. Some of them are automatically unlocked by progressing the story, others can be missed. For this achievement, you need to collect all the optional ones.

There are 4 optional [Ex] pages. In order to get them...

• Talk to Nobara during the optional investigation in chapter 1.
  
• Talk to Mika during the optional investigation in chapter 1.
  
• Talk to Momoko during the optional investigation in chapter 1.
  
• When Taiko asks for your opinion in chapter 3, shortly before the interrogation, answer him truthfully. This will give you an extra scene in chapter 5, which will unlock his [Ex] page.

For this achievement, you basically have to do two things: unlock all optional Trivia entries in the Notebook (please refer to the Tenacious Trivia Nut section of this guide), and finish chapter 5 after picking the true culprit, as this will unlock the final diary entries.

All you have to do for this achievement is to reach a Bad End. There are various ways to do so, and a total of 4 different Bad Ends you can get. Below is a list explaining how to reach all of them.

• During the very first choice of chapter 5, pick: "Maybe so, but..."
  
• Alternatively, when asked to present the culprit after the above choice, present either Hiro or Runa for two different Bad Ends.
  
• If you chose to present the true culprit, you can still get the first Bad End by picking "Yes, she cannot escape the guilt of that, but..." in the following choice.
  
• When asked to present the mastermind, you can also present anyone but Kamen, Momoko or Runa in order to get yet another Bad End.

This achievement will be unlocked in chapter 4, if you manage to save Kotoba's life.
In order to do so, you will need to make the right decisions so that Raiko and the rest of the group can get to him ASAP, reaching him just in time to prevent the worst :

• When Taiko and the others leave the dining hall to get to the basement, try to stop them.
  
• Afterwards, when they decide to use the window to get into the breaker room, propose to head into the employee quarters.

The achievement will be unlocked shortly after the fire has been extinguished by Rie and Taiko.

To get this achievement, you need to view Extra Scene A in the Extras after finishing the game. In order for it to become available, however, you need to get a Detective Rank of S or higher, which would mean scoring at least 33 Detective Points or 82,5%.

You will get this achievement after reading Kamen's Diary B in the Extras section after finishing the game. In order for this diary entry to get unlocked, however, you will need to do the following:

• During the optional investigation in chapter 1, talk to Kamen.
  
• For the first choice, pick the second option.
  
• For the second choice, pick the first option.
  
• Now, continue with the rest of the game and pick the true culprit in chapter 5. When you are presented with the final choice of the game in the epilogue, pick the first option.

To become the Ultimate Detective, you will have to beat the game with a perfect score of 100%, which will grant you an S+ Rank. This means giving the correct answer and presenting the correct culprit/evidence on your first try every time. No mistakes allowed.

There is a total of 40 instances in which you can gain a Detective Point. I will divide them into chapters and tell you exactly what you need to do to get all 40 points.

Chapter 1:

• In the hallway, after receiving the map from Rie, when Raiko states the total number of guests that can stay at the resort, pick: "...fifty guests."

Chapter 2:
When Raiko tries to calm down the paranoid Nobara in the hallway, on their way to the breaker room, do the following:

• Present Rie as the culprit.
  
• Present "Corridor Candles".
  
• Present "Locked Rooms".
  
• Present the "Resort Basement" map.
  
• Present the "Resort Basement" or "Resort 1st Floor" map.

Chapter 3:

• During the first choice at the beginning of the chapter, pick: "At the reception!"
  
• In front of the breaker room, when talking about the rope, pick: "She openly carried it with her the whole time."

Chapter 4:
At the beginning of the chapter, when Raiko thinks about the most likely suspect, do the following:

• Present Hiro as the culprit.
  
• Present "Questioning Results".
  
• Present "Resort Keys" or "Locked Rooms".

Once everyone starts rushing to the basement in order to look for Kotoba, do the following:

• When Taiko and the others leave the dining hall, pick: "...tried stopping the others!"
  
• In front of the breaker room, when talking about the window, pick: "It's definitely open now!"
  
• After they decide to check the window, pick: "Let's head into the employee quarters!"

Chapter 5:

• For the first choice at the beginning of the chapter, pick: "No, she didn't." (this one does not grant you a Detective Point, but it is necessary for the True Culprit Ending)
  
• Present Momoko as the culprit.
  
• Pick "No, she didn't kill anyone." (this also doesn't actually give you a Detective Point)
  
• Present Momoko as the mastermind.
  
• For the next choice, pick "...Momoko died first."
  
• Next, pick "No, that's impossible."
  
• Pick "She actually had multiple accomplices."
  
• Pick "She had to have three."
  
• Present Kotoba as the final accomplice.
  
• When talking about the second floor guest room, present Hiro as the culprit.
  
• Pick "I have a witness."
  
• Present Mika as the witness.
  
• Present "Glass Table".
  
• Present "Glass Table" again.
  
• Present Kotoba as the culprit.
  
• Pick "Something was stuck in the lock."
  
• Present Hiro's Body.
  
• Present "Red Rope".
  
• Present "Halloween Sign".
  
• When talking about the guest room confusion, click on Room 209.
  
• Pick "...inwards."
  
• Present "Drawer".
  
• Present Momoko's Body.
  
• Present "Witch Costume".
  
• When asked which part of the costume to present, pick "Present the cape".
  
• Present Momoko's Body.
  
• When talking about the fire, pick: "She wanted to create a distraction".
  
• Present "Intercom".

If you follow these instructions, you will get the Ultimate Detective rank upon finishing the epilogue. Keep in mind, however, that you really need to get everything right on your first try. If you present an incorrect piece of evidence before the correct one, you won't earn a Detective Point for that instance!

If you want to unlock this achievement, you have to finish the game with 0 Detective Points. This basically means giving the wrong answer every time, and always presenting an incorrect culprit or a wrong piece of evidence before showing the correct one.

Please refer to the Ultimate Detective section of this guide, where all the correct answers are listed. Simply choose the wrong answers instead and present anything but the correct culprit/evidence before presenting the right one. Be mindful of the following 4 instances, however:

• During the first choice at the beginning of chapter 5, you have to pick "No, she didn't." Otherwise, you won't be able to finish the game and even get a Detective Rank. Because of this, answering this one correctly does not grant you a Detective Point.
  
• When asked to present the culprit right after the choice above, do not present Hiro or Runa, as this will lead to a Bad End. Pick any of the others first and then Momoko as the true culprit.
  
• During the next choice, you have to pick "No, she didn't kill anyone." (same reasons as above).
  
• When asked to present the mastermind, choose Kamen or Runa first, before presenting Momoko as the true mastermind. Picking anyone else will lead to a Bad End.

This section will give you an overview of all the unlockable extras of SHINRAI and how to get them. Some have already been covered in the achievement descriptions above, but I will mention them here again, just for the sake of completion.

Unlockable CGs:
There are only two CGs you can miss.

• Talk to Nobara during the interrogation in chapter 3 to get the Consolation CG.
  
• You can only get either Conflagration A or B in one playthrough. For A, you need to save Kotoba. For B, you need to arrive too late to save him. Please refer to the Just In Time section of this guide in order to see how he can be saved.

Unlockable Diary Entries and Extra Scenes:

• To unlock Extra Scene A, please refer to the Secret Maneuvers section of this guide.
  
• To unlock Kamen's Diary B, please refer to the Unmasked section of this guide.

Unlockable Character Profiles:

• For Kagayaku's Character Profile, view Extra Scene A in the game's Extras.
  
• For Kaleido's Character Profile, view Extra Scene A in the game's Extras.
  
• For Yuuichirou's Character Profile, view Extra Scene B in the game's Extras.
  
• For Nobara's, Mika's, Momoko's and Taiko's [Ex] pages, please refer to the Prolific Profiler section of this guide.

Unlockable Trivia Entries:

• There are 5 in total. Please refer to the Tenacious Trivia Nut section of this guide in order to see how you can unlock them.