Kanon's death in the boiler room

Axioms

All of the survivors have alibis! Let us include the dead as well!! In short, no kind of human or dead person on the island could have killed Kanon!
Kanon did not commit suicide
Beatrice refuses to repeat that it was a homicide.
Kanon did not die in an accident!

An interesting piece of narration about the boiler room

It isn't clear when Grandfather's corpse started burning in the incinerator. Since, according to Genji, the strength of the flames hadn't been that strong, the body must have started burning a long time ago, so that stench could slowly creep out of the furnace and fill the room bit by bit, eventually pouring out and climbing up the staircase. Putting aside whether he was rare or well-done, Grandfather had been brought out, killed, and burned... even though he had started out locked away in the closed room created by his auto-lock. There's probably no doubting this...

However, according to Genji-san, the boiler room is usually locked. The possibility that someone outside our group had snuck in and committed the crime was overwhelmingly high, and there was also a good chance that this person was walking around with something like a master key. After all, the doors and windows throughout the mansion had been checked. But despite that, the culprit was able to strut around the mansion freely.

Corollaries

The first red basically translates to "it was not a homicide", unless the perpetrator is not technically a survivor, or is not a person on the island.
What about the closing door Kumasawa and Kanon heard from the basement?
Just like with the murder in Eva and Hideyoshi's room, we can't trust the unreliable narration to accurately describe a scene with only the servants present.
"According to Genji-san the boiler room is usually locked."
Nothing according to Genji is reliable.
"After all, the doors and windows throughout the mansion had been checked."
By the servants and Natsuhi. We think Natsuhi is innocent but they might have split up.

Kanon did not die... at all!

No need to assume he died in the boiler room in legend, they could just as easily have faked it.

Leads:

Kanon supposedly pulls out the stake from his chest before being found.
They had plenty of fake blood to make the magic circles.
Beatrice refuses to repeat that it was a homicide.
We already think Nanjo is lying.
We couldn't figure out another way around the red.

Obstacles:

Jessica supposedly witnessed his death because she was taking care of him the whole time, but she also would have believed the doctor in the room when he declares someone dead.

Here's a super obsolete theory from before we ironed out the details of our Sayo conjecture, and Kanon was still a separate person.

Kanon wasn't in Rokkenjima

Shannon survived the first twilight. She took on Kanon's identity who by that point was no longer in Rokkenjima, and was the person killed in the boiler room.

Pros:

We can claim that Kanon left the island and was killed by someone, or he's was never on the island at all and survived.
We get down to 16 people and can have a culprit X for all the murders.

Cons:

What happened to No one else can go by Kanon's name! ? (we actually had kind of a work around but it was a stretch).
Nanjo is still lying in this theory, he wouldn't mistake one for the other while examining the body.
If we claim Kanon is already dead like Kinzo this needs to hold for every episode, but it at least is definitely false in Alliance.
"No one escapes, all die." Gets in the way of him leaving the island after being there.

Oh and let's not forget Kinzo was here too.

Kinzo's burned corpse

Kinzo's body was burned in the incinerator recently.

Leads:

First things first, because the identity of all unidentified corpses in Legend has been guaranteed in red, that is indeed Kinzo's body.
The body couldn't have been burning for longer than several hours or a day at most, or they would have noticed the smell a lot sooner.
It's unlikely they left it to rot in the studio it must have been stored somewhere such as a coffin in the chapel.
Or maybe it was in the boiler room but it was only incinerated later.

The servants burn Kinzo in the boiler room

The servants are trying to push the narrative of magical murders, so they slowly incinerate Kinzo so that his body will be found with a delay.

Leads:

The gross smell is always going to lead to someone discovering the body eventually. Burning the corpse is something you should only do if you plan for it to pop up at some point.
Either they move it, or maybe it really was placed there by Krauss to hide it, and all they do is turn on the heat.
In Turn, Kinzo was simply never designated as a victim, perhaps due to [REDACTED].

Obstacles:

It's hard to believe Genji would do something like that to his former master... unless he believes his new master to be someone with equal or higher authority, someone like Beatrice.