I admit, going in, I was not entirely sure why Toa's route had to be the true one. While we certainly were left hanging on a number of things regarding him (the voice that called out to him in the dark, why the Ensepulchers thought he was a revenant, why it would be "too late" if he held his concert at a later date, and him leaving town early on Sosuke's route), he himself did not feel that mysterious and his story ends in as satisfying a manner as anyone else's.
As far as learning the truth about anything, his route is wedged in between the intro scenarios of Hino and Isora, and the heavily lore-filled episodes of Sosuke and Yuzuki, but in tone it felt a lot closer to Hino and Isora's. Revenants are still a local legend, though some people clearly believe they're real, but we don't end up confronting one by name in the Normal and Good Endings. Also, his route is the one that touches the least on Ichiko's brother as she doesn't do any investigation in favor of hanging out with Toa.
And on that front we don't get many more answers, but Toa's true route clearly knows it's our primary cast's last hurrah, and does an admirable job of bringing everyone together.
Back at the hotel, Toa is patched up by Sosuke, just like in the regular version of Toa's route, but everyone also meets in the cafe to discuss Tsukuyomi's final words and the fact he claims to not to have killed Sosuke's father since he only kills women.
Other facts come out that make it clear that certain events on other routes happened even though this story is mostly following Toa's route. For instance, it doesn't surprise other characters to know that Sosuke's father was killed, whereas the second victim's identity was never revealed on Toa's route. And more comically, the optional scene where Ichiko walks in on Hino in the men's bath is referred to as something that happened earlier in their stay.
The group is sympathetic, but Yuzuki blocks everyone from leaving, because there is an easy way to tell whether or not someone's a revenant. At first it sounds like he means the mark that Sosuke had previously brought up on Toa's route. Each time a revenant kills someone they're supposed to get a mark on their back, and Toa didn't have one, therefore he couldn't be a revenant. But Yuzuki says there's a simpler way than having everyone strip down (and to be honest, his way is pretty effective).
Interestingly, Yuzuki does not suggest bringing out the salt (probably because he's only interested in identifying the revenant and not killing them if he doesn't have to) and he says that they'll use Isora's lighter and each person will put the flame up to their body for a few seconds. Just enough for the skin to turn red. But before they begin, Yuki asks one last time for the revenant to identify themselves before people start giving themselves minor burns, which reveals a surprise when someone responds.
I thought it was going to be Toa. (They have nice reaction shots from members of the cast so you have time to think about it) Given that he was already suspected of being a revenant and this is his true route, it made the most sense, but it was Yua, and the game does a credible job of raising the possibility that Yua could be another revenant. She's the only character without an alibi for the night of Shinryu's death and she admits pushing him off the cliff behind the shrine.
(I can't believe how much I liked Yuzuki in this scene. His behavior is expected on his own route, but he's super hardcore on Toa's true route, which makes him look freakin' crazy to everyone else. I was reading all his actions with a stupid grin on my face.)
This reveals Toa as the revenant and Yua is an ordinary human. We quickly find out that she's his sister, which is why she was covering for him, and that Toa is another peaceful revenant whose one remaining wish to perform his first solo concert in his hometown. (Yua did kill Shinryu though. She was only covering for him being a revenant.) It's been difficult for Toa, but by being close to Ichiko he has managed to stave off his hunger pains as a revenant (for reasons we learn later), and learning that adds a little more meaning to all the recharges he asks for when he hugs or kisses her on his regular route. It's not just for affection, but she's what is literally keeping him going.
This isn't as hard for everyone to buy into as it sounds, since it turns out at that all the hotel employees and remaining guests are fellow Supernatural Club members (save Karasuma who is conspicuously absent in this scene) and Yuzuki has made it his new life's mission to help revenants peacefully pass on.
Thus we have all the major cast members working together to convince Toa's manager to not cancel the concert, to get Toa to the venue without being captured by the Ensepulchers, and ultimately make his first and final performance as a solo artist.
This also means that the true ending of the game is bittersweet. Even though Toa was reunited with his childhood friend, Ichiko, they have to part since he has no time left. It is a beautifully rendered passing, with Toa dissolving on stage after he finishes his performance, but I wish there had been a little more after that.
Also oddly, though "true" appears in the route name, it is literally just the True Route specifically for Toa and not the final route of the game. It wraps up who killed Shinryu Tatehira and who the last revenant is (as well as explaining some common route weirdness with Yua's behavior and some of the Toa route exclusive mysteries).
We don't learn anything more about Ichiko's brother though, but completing Toa's true route unlocks the final route, which is Hanate's.
As a final note on Toa though, his True Ending breaks continuity with his Good Ending, where he and Ichiko say good-bye when she needs to head home after the cancelled concert. They promise to meet up again, but obviously this can't happen since Toa is a revenant existing on borrowed time. So if one replays his Good Ending after unlocking his True Ending, there is an additional scene after she gets home in which she receives a letter of apology from Toa, who explains his predicament and that by the time she receives his message he'll already be gone. He thanks her though and says that he thinks he came back to meet her again, implying that he won't revive another time.
Though I didn't dislike this route because the primary cast got to reunite and everyone's backstories were no longer hidden, it's very clearly a fanservice send-off and doesn't really add anything to the overall story. The scarlet Violacia tease at the end of Yuzuki's route has nothing to do with Toa's true route.
In fact, if the game had made it so Tsukuyomi killed Shinryu instead and made the vigilance committee's suspicion of Toa a legitimate mistake (with reasons to see how that could have happened) it would be possible to cut this route with minimal losses, and it might have allowed for a stronger game.
The reason I make this suggestion is because Hanate's route isn't well put together and suffers from either a lack of planning, a lack of budget, or both. Though it's not the full cast party send-off Toa's true route is, I would have gladly dumped the fanservice it if meant making Hanate's story a full blown, proper route. We'll get to why next week!