Ok I've read the lyrics and like. I think there's a lot of stuff going on here but I really like that the message of this song at the end is one of self acceptance.
Even your mistakes, even your pain, even your despair, they're worth feeling, and acknowledging that will make you whole. If you feel nothing, if you feel empty, you can fill yourself with the things you love, with the people you love. If you look at a past self you forgot, you can embrace it and make it a part of you again. Even if you were lonely before, you can accept the company of those who are with you now.
Even if you're okay now, the pain it's also a part of you, and you must face it again.
It's a never ending path Tsukasa and we all walk over and over again, because you can't just repress the negative emotions forever just because it's complicated and uncomfortable for those around you. You can't live a life without those feelings. The unfair thing here it's that Tsukasa was supposed to learn that as a kid, but didn't have the support he needed because his circumstances were complicated, and now he has to unlearn years and years of repressed feelings. The good thing is he doesn't have to do it alone.
I also find it very interesting how Rui, of all people, is the one trying to reassure the other 4 that they're not alone and they'll overcome this too, when Nene and Emu are singing about the same despair Tsukasa is feeling. I also like that every time youngkasa appears on screen, Len is the one singing. That also ties w his symbolic stand-in of youngkasa in the story.
Btw I love this song being called "all in one". At first I thought it referred to Tsukasa being an actor, someone who can play different characters and also become different people (which is the conflict here, he's trying to become William, in a way), all those personalities, all those stories to tell, "all those possible realities in one person", but then I thought it meant he was trying to embrace all his emotions and memories, instead of just trying to be happy all the time he'd experience "all these feelings in one whole person". But then. The heart scenes in the mv. Wondasho are giving parts of themselves to Tsukasa, they're giving him their hearts (omg the polysho propaganda it's strong w this one) and he, as the leader of Wonderlands × Showtime, is all of these people at once, because now they're a part of himself, and he is all in one.
Idk man it's just so beautiful, everything about kasa7 is fucking genius I want to kiss the brains of everyone involved w this bc that's just crazy awesome.
Live laugh love Tsukasa Tenma.