Case Discussion
I'm gonna skip summary,...
The culprit is most likely
Ashizawa Sumito.
The plan was to make the victim seem alive while the fire started, in order to make it look like an accident. How he did it was by using a trick to make him move up and down to make it seem like he was awake and squating. What he needed for the trick was what Rumi hinted at towards the end of File 988, the science behind a balancing toy.
The reason the balancing toy is balanced is because the center of gravity, which is on the two sides, is below the point of support, meaning that most of the weight is equally distributed on the two acorns on the sides, and they are both underneath the level of Ayumi's finger. This makes it so that even if you push down one of the acorns on the sides, the toy won't fall down, but instead sway up and down until it retains its balance and stays still.
In this case, he set it up so that they could create the same effect, where Urushibara(the victim) was sitting in the position that would be equivalent to one of the side-acorns in the balance toy(that moves up and down when balance is disrupted), to fake his squating. For Ashizawa to create that same effect, he would need something that will be placed on the position of the other side-acorn, that equals to Urushibara's weight. The only thing that could've been used is what Furuoka had brought with her for Urushibara, the manga volumes. Sake is flammable, so it was most likely poured on the stack of manga volumes, so that they would burn away faster when the fire started.
The other candles were sticked together, using the skewers from the dango side-dish as the bond, so that they would form the shape of a block. It's position in the balancing toy would be equivalent to Ayumi's finger. The laptop, that was next to the magazine, was bent like a "V" and placed on top of the candle block. A certain flammable bent object(that will carry and connect the chair with the manga volumes like a scale) was placed on top of the laptop, and then finally the lantern on top of that object.
After Ashizawa constructed something similar to this, he just had to disrupt the balance(making Urushibara and the volumes swing up and down), and then leave and act like the lights just turned on, as if Urushibara just woke up. The gradual "harsh squating" that Danno noticed was from the fact that the swinging distance decreased as Urushibara and the manga volumes reached a balanced state(making it look like quick smaller movements). Those harsh movements is what most likely lead to the lantern falling on Urushibara and burn the tent(like for example, making some of the volumes fall so that the weight balance disappears and the impact of the chair falling hard to the ground makes the lantern fall off).
The magazine was placed under Urushibara. his bent legs covered the area of the magazine so that it shaped a "V". It's purpose was to burn-up, the moment the liquefied candle wax spilled on it, and lead the fire to Urushibara's clothes(which is why the burn mark didn't reach where Urushibara's legs covered). Sake was most likely poured on the magazine as well.
Conan noticed that the band-aid/tape on Urushibara's fingers were on the wrong fingers(left hand) and wanted to confirm with DB. That's because Ashizawa taped together Urushibara's fingers with the band-aid/tape so that it would look like he was holding his hands behind his head to do squats. All that was left is to let the fire burn the tape so that his hands naturally falls down.
The fact that Urushibara didn't notice anything during the setup is because he was asleep after getting drunk, as Furuoka mentioned. Ashizawa himself mentioned that Urushibara never woke up when they pulled pranks on him while he was asleep.
The evidence to him being the culprit is probably the stain/dirt on Ashizawa's right elbow. He got it the moment he came back after "checking on" Urushibara. As he was constructing the trick, his elbow probably touched the spilled sake on the ground while he was bending down to put the magazine(or the unknown flammable object) under Urushibara. This would prove that he entered the tent when it was supposed to be closed(which it wasn't). The reason the zipper was later found locked was because Ashizawa most likely locked it after the tent burned down, to make it look like it was closed all along.
The motive was probably his fear of losing his chance to get scouted, like Danno did, because of Urushibara's instigated "accident". Urushibara's threat was probably taken seriously. The real reason to why Urushibara hurt Danno was probably because he wanted to help him get close to Furuoka, since Danno probably revealed his crush on her to him. He probably didn't intend for it to get that bad. The reason the girls stopped approaching Danno was probably because Urushibara told them off so that Danno and the manager had a chance(which Ashizawa mistook as it being due to popularity loss).
Plot Discussion
The plot intensifies, as we get the first meeting of two important plot characters, Kuroda Hyoue and Wakasa Rumi. Conan followed up his suspicion on Rumi by revealing that he's aware that she has been leading him to cases(as I mentioned in my Rumi discussion) and that she is someone with a hidden agenda. After that however, the first new suspicious thing we got was Rumi's reaction to the word "prosthetic" and Haibara's BO sense getting triggered by her, followed by Rumi gripping her pocket(File 987).
Rumi's serious reaction and gripping suggest that she was hurt by something related to "prosthetic". This heavily suggest that Rumi has a grudge on Rum, meaning that she is aware of his prosthetic eye. Conan noticed that something inside her pocket was being gripped. It's most likely connected to her grudge, like a memento of someone Rum has hurt/killed. Haibara also seems to have finally reawakened her BO-sense(although it still hasn't been addressed) and getting triggered by Rumi suggests that she's connected to the BO. This does imply that she is, or was affiliated with the BO, and it's clearly Gosho's way of making Rumi look like Rum(who she most likely isn't).
At the start of File 987, we see Kuroda investigating the Kohji case and connecting it to Rumi's news headlines. Since he was looking at the dying message the focus was most likely on Rumi's name, which is clearly based on the letters from the dying message. His strong interest in the Kohji case suggest that he was most likely involved somehow. After finding out that Rumi was going to a campsite, he makes the remark that going camping is unlike "that person".
Kuroda's remark suggest that he's assuming that Rumi is the prime suspect of the Kohji case, Asaka, who is suspected to be Rum(based on the dying message). It looks like he was being playful with the idea that a criminal like Rum is camping. Considering that Gosho portrayed Kuroda as a none-BO-person(since Haibara didn't sense anything from him), it's safe to assume that he is continuing with that portrayal, but also adding the idea that Kuroda is Rumi's enemy and that Rumi is Rum. This is clearly shown through their interaction through out File 988. In reality though, this is most likely a red-herring, and the reality is just that Kuroda is suspecting her to be Rum, when she isn't. In Rumi's case however, we see her getting spaced out and showing vulnerability as she's glaring on Kuroda, to the point that she doesn't notice Ayumi's call(File 988).
This once again looks like Gosho's way of making it look she recognized Kuroda, who is Rum's enemy(as if she's Rum). From the information that we have gotten however, the more accurate assumption would be that she reacted to him recognizing her and indirectly saying that he suspects her to be affiliated with criminality(since he asked for her permission about calling the police). Rumi has shown to be very intelligent, so her being in deep thought could be her wondering why this scary-looking guy is interested in her, since she clearly hinted at her being aware of Kuroda's true goal being her.
Considering that Rumi intentionally created the "Wakasa Rumi" name, with the Kohji case in mind, it makes sense that she would suspect Kuroda, who has shown that he suspects her to be Asaka, to be someone involved in the 17-year-old case.
When Rumi snapped out of her deep thought, she acted very suspicious, which Haibara picked up. Rumi was looking around, as if she didn't know where Ayumi was calling her from. Haibara interpreted it as Rumi possibly not being able to see with her right eye(File 988).
This is, once again, Gosho's way of making Rumi look like Rum(who can't see with one eye due to having an artificial eye). Right after that however, Conan had his own thought process about Rumi's behavior. He was suspecting that other than her "accident" with the folding screen, her clumsy behavior might not be an act. The interesting thing about this is that we didn't get to see Conan finish what his suspicion was. This looked awfully a lot like one of Gosho's mislead tactics, where he is trying to make us think that Conan has the same suspicion as Haibara(similarly to how he wanted us to think that Wakita is looking at the same news as Kuroda). Conan has always been the character that always follows with the right suspicion(when his thoughts are ambiguous). This heavily implies that he isn't suspicious of Rumi's eye not working. From the start, the idea that "misjudging the distance from certain objects means you're one-eyed" was flawed. The most probable reason to why Rumi would misjudge the distance to the teachers desk or the basement door(and therefore bump on it) is if her glasses have the wrong strength-level(relative to her). This was shown clearly in File 2 when Conan wore his father's glasses to disguise himself and couldn't see anything(in the anime, he even bumped his head like Rumi).
This implies that Rumi isn't used to wearing glasses, similarly to Conan, when he tried to disguise himself with it. This is most likely Gosho's second implication that "Wakasa Rumi" is a disguise(following my Rumi discussion), which further points her to being Vermouth in disguise(adding to the fact Haibara sensed the BO from her). Similarly to how Wakita might be on to Conan(from my Wakita discussion), it looks like this is a setup to Conan being on to Rumi's true identity(Vermouth).
;P
