Ding-dong, the witch is dead.
Full Solution
The culprit is Battler.
Before Crime
Battler and Rudolf arrive at the mansion. Rudolf has a plan – to find Kinzo’s will (which he believes is on the island) and replace it with a forgery in which Kinzo’s fortune falls to him. Due to Kinzo’s failling mental condition and memory, all Rudolf would’ve really had to do was go and bribe the two witnesses, securing them a piece of the fortune.
Before they arrive for the conference, Rudolf gets in touch with Okonogi to look into the mansion’s architecture for potential hiding places. Okonogi doesn’t find much besides the secret of Kinzo’s tower – that there’s a mechanism activated by pressing a specific stone (34th stone from the right and 3rd one from bottom) that causes the tower’s secret to be revealed:
It’s 13 meters high, not 9. The ceiling is merely placed on 9 meters.
Rudolf doesn’t think much of it, but keeps it in mind if he needed it in the future.
- Note: You could’ve also assumed Rudolf merely wanted to find and look at the will, then do whatever with it. Rudolf would’ve found out the names of the witnesses from the original will (which, I believe are always noted somewhere). But since that’s an assumption you would’ve had to have made, it’s much easier to just assume he wanted to get the original for whatever reason. It’s not a big deal in the long run and I would’ve accepted any explanation. Motive wasn’t the most important part here, anyway.
And indeed, he ends up needing it. For at dinner, Kinzo announces his bizarre challenge.
Rudolf realizes that, having read the weather report, that the upper part of the tower (the one above 9 meters) would’ve been filled to the brim with water. If Rudolf triggered the ceiling’s mechanism, the water would’ve come falling into the tower. Rudolf would’ve then used the chair to reach the window (either by climbing on top of it as it floated on water, or turning it upside down and placing the seat on the lower flat part of the window).
In preparation for this, he prepares a spare set of clothes. He doesn’t need anything else but that.
The ultimate goal is simple – due to the fact that Kinzo would’ve been in the passageway guarding the tower, there would be nobody in his study for a change, allowing Rudolf to find the will.
After making the switch and bringing the witnesses, it didn’t matter what happened next.
Kinzo would’ve died eventually – if the water in the tower had drained by the time the two days were up (through the toilet), Rudolf probably figured he could sneak back into the tower (despite it being denied in purple, that’s merely what he believed what he could do), and get Kinzo to keep his end of the bargain.
Alternatively, Kinzo could’ve opened the door earlier and being the weak old man that he was, and being that he was stuck in that passage, probably drown in the water.
Or simply let things be, get chewed out by Kinzo for escaping the tower, but with the old man was going to die soon anyway. Kinzo wouldn’t have bothered checking the will to disinherit Rudolf because… well, Rudolf was never in the original will (as you will discover shortly).
Rudolf’s Escape
The escape goes off without a hitch. He reaches the window. He then jumps to the roof, lowers himself down to the passageway and hops down from the passageway. His bruises are not the result of this. He takes no damage during this.
He then sneaks into Kinzo’s study through the window he’d secretly left open during his meeting with Kinzo in the study at the beginning. He then changes his clothes to a dry set (remember, he’d prepared it before entering in his backpack).
He ransacks the office and finds the will. Overjoyed, he makes the switch.
Something unexpected happens, though. As he’s putting things in the office back in their place, the metal box falls on his head.
Rudolf’s Death
Rudolf, not knowing how bad the injury is, but sure as hell feeling it, realizes he has to get to the medical office. He can’t exactly scale the mansion, so he has to get there by foot. It feels like he’d taken a bad hit, though.
So, he realizes he has no choice.
He dons Kinzo’s trenchcoat and hat and makes his way upstairs. He’s dazed so he doesn’t immediately notice Kanon cleaning. Kanon calls out to him and Rudolf begins to run. He reaches the top of the stairs and continues to run.
While Kanon falls and loses consciousness, Rudolf doesn’t know that. He doesn’t stop to look behind him. He keeps running. Going to the medical office or the cousins room is a dead end. Window’s closed too. Going straight is a no-go, either. He can only turn the other corner, towards either Jessica’s room, Krauss’ room and the open window. We know he never went into the first two options.
So the window it is.
The problem here arises when it comes to Rudolf’s injuries. Had he simply jumped out of the window, he would’ve simply fallen normally without much damages – it was only one floor above.
So, what happened?
He must’ve slipped and fallen.
On what?
On the marble Battler ended up dropping earlier when he fell while getting the games.
• Note: In spite of this, I would’ve accepted him simply jumping out and you saying he got his injuries from there. In that case, though, the marble would’ve had to have been dropped somewhere in front of Bedroom 1.
As he falls on the marble, his body is launched forwards towards the window, with his foot pushing the marble backwards. Rudolf falls out and receives his injuries. The marble rolls across the hall, in front of Bedroom 1.
Rudolf crawls back into Kinzo’s study and throws the coat out of the window, explaining why there was no rain on him. Without being able to leave or go anywhere, with his injury to the head and without the strength to go anywhere else, he dies.
• Note: There are some variations I would’ve accepted and I’ll get to those later.
Battler didn’t kill Rudolf, Rudolf’s death was an accident.
Nanjo’s death
Battler did kill Nanjo, albeit without intent.
As he walked outside of Bedroom 1 to patch George up, he saw the marble that had found its way in front of the door. Annoyed over the previous argument with the cousins, he kicked it. Jessica never saw it because she was focused on Battler getting the med kit and George’s screams covered up any sound the marble might’ve made while rolling.
The marble went into the vent, down below into Nanjo’s room, into Nanjo’s mouth, suffocating him in his sleep.
Battler would later be mystified as to how Nanjo died himself.
Clean-up
As they searched for the mystery man, Battler looked out the window and saw his father, crawling to the window, and lied over there not being any traces of him being there.
Everyone goes downstairs to the study, and Rudolf is found. Battler is the first to step into the room (and there is proof of this later). This is where possible variations are possible depending on what you decided Rudolf did before entering the window.
- If Rudolf crawled in, and dropped his coat inside of the room and didn’t close the window, at this point Battler takes care of both.
- If Rudolf didn’t close the window, Battler simply closes it.
If Rudolf had taken off the coat himself after entering the room and thrown it out, there’s no contradiction in the explanation as to why he didn’t get wet.
If Rudolf had taken off the coat directly before reentry, Battler’s purple about Rudolf’s clothes being completely wet can be a lie.
Alternatively, the lack of rain can be explained by a mixture of Battler’s purple about the clothes being a lie, and a possibility that the rain had only begun to fall heavily after Rudolf got into the study. (Natsuhi’s purple, after all, was referring to the current downpour and based on her observation after looking out of the window at the time.)
This section wasn’t terribly important, just wanted to cover some oddities.
Kinzo’s Death
The only person Battler intentionally killed was Kinzo.
How?
It’s simple. He wasn’t part of the group known as ‘cousins’.
And I mean that legally, biologically, and in terms of narrative.
Biologically he was not a cousin because Rudolf was adopted. There were hints about this through the fact that Rudolf’s childhood bedroom simply does not appear to exist. Jessica’s room was actually Bedroom 2 (after all, if there is bedroom 1 there must’ve been a bedroom 2) and there are no other rooms that could’ve been bedroom 2 (Nanjo’s room was always there, the medical office was Kinzo’s bedroom). An additional clue is Kinzo’s strange narration on the opening:
“I always knew he would be the end of me.” Kinzo thought, feeling somewhat pleased with himself. “It would appear that, in spite of everything, the defining characteristic of what it means to be an Ushiromiya was instilled into this man’s heart. He is truly my son. Perhaps ironic that, out of all of them, it would’ve been him to take this gamble. Then again, Eva and Krauss are too prideful for something like this, and Rosa is too weak to even think of it.”
Thus, Battler is not biologically related to the cousins (this is not necessary to have been picked up on, though).
Legally he is not a cousin because Rudolf leaves the family register. He never reenters it – Kinzo had only welcomed them to the conference with open arms, but not into the family. (You will find this detail interesting, because it means had the original will gone through, Rudolf would’ve ended up with jack shit.)
Narratively he is not the cousin. At no point does the narrative refer to him as one. In fact, it makes a clear distinction at times:
Aside from that, nothing was particularly different. Rosa, Eva and Krauss were sleeping in their own respective rooms, and the cousins had all decided to go into, as Kinzo had dubbed it, Bedroom 1, a spare bedroom that had later been repurposed to serve multiple guests.
Rudolf would be sleeping over in Jessica’s room. Battler had also elected to share the room with his father. Rudolf could tell, however, that the boy would inevitably spend the night in Bedroom 1 with the others.
Battler walked over to the cousins
Of course, there were parts meant to distract you, such as:
The cousins quickly patched George up.
Rosa and the cousins stood at the door.
That last one in particular is important because once you know Battler is not a cousin, you know he wasn’t at the door. Directly at that scene though, he does speak as if he’s present with everyone else, meaning he could’ve only been inside of the study (where he could’ve done the clean-up).
(And, uh, just to note, this purple:
MARIA / “Uu… Maria moved a bit slower, so nobody rushed ahead or anything.”
Was referring to people going downstairs, not regarding anyone going into the study first – although I think most of you assumed as much anyway).
With this, Kinzo’s death becomes simple. Battler isn’t included in these purples:
JESSICA / “I can confirm that much. Aunt Rosa and all of the cousins have been together since we came down to the ground floor.”
GEORGE / “Seconded. Aunt Rosa and the cousins never split up after Rudolf’s body was discovered.”
And simply walked off while everyone was distracted with the body, went to the servants’ room, killed Kinzo, took the key, and left.
Now, as for his motive for doing this.
Battler was in on Rudolf’s plan from the start. If you re-read this section:
BATTLER / “I really don’t want to have this conversation right now. You’ve had all year to remind me that we’re doing badly.”
RUDOLF / “We need the money.”
BATTLER / “I just said – you don’t have to remind me. And yeah, I know. But not like this. Say that you do it. What if once he offs himself, we find out that he had a will locked away in some bank that says he’s giving everything away to charity?”
RUDOLF / “He’s too prideful for that. He has the same detest for the outside world as he does for each and every person in this house. Trust me. It won’t be that.”
You’ll realize Battler was expressing concerns over the will not being in Kinzo’s mansion in the first place and that Rudolf’s entire gambit is a waste of time.
After finding his dad’s body, he realized he was more or less fucked.
- He didn’t know if Rudolf had successfully switched the will or not (because all he knows at that point is that there’s something on Rudolf’s person, but not which will it is – the real or the fake), or if he’d even found it. (And even if he had, Battler wouldn’t have known who the witnesses were, so bribing them himself wasn’t really an option. OR, if Rudolf really had switched the will, Battler had a shot of bribing the witnesses… but only after killing Kinzo and then finding out who they were.)
- If Kinzo was left alive, he would’ve undeniably realized Rudolf’s plot and thus probably ensured Battler would never see a dime. With Kinzo’s death, however, he would be able to have an excuse to maintain a relationship with the Ushiromiya family through cousins if nothing else, and ensure some fortune sees his way down the line.
- If Kinzo is left alive, people will enter the tower and realize Rudolf’s trick and his original intentions. Same scenario as before.
- Note: Explanation 1 wouldn’t apply if you went down the route of Rudolf simply wanting to steal the original, obviously, but it’s not a terribly big deal in the long run – Rudolf stealing the will in the first place would’ve been treasonous enough to the family in Kinzo’s eyes. Or so Battler would’ve believed.
And let me tell you, your boy Battler really needed that money.
So he killed Kinzo, took the key to the tower, ensuring nobody enters and discovers Rudolf’s trick (as mentioned earlier, the water would’ve probably drained through the toilet later).
Later, after Nanjo was found dead, he decided to tie everything up by accusing Gohda – the perfect victim of chance.
I’d originally considered making Genji the guard, but with him being the first witnesses to the will and Nanjo being the obvious choice to the second one, it would’ve hinted at premeditation far too much if it started to seem Genji was being intentionally framed. By having it be Gohda and Genji just kinda left… floating, it would’ve created a question of the culprit’s motivations and thus lead to the possibility of the culprit not being intentional in their murders.