My take on it is that bro used to see them on a pedestal but now he's slowly envisioning stairs leading up to that pedestal. He doesn't go up those stairs because he feels he doesn't need to but he has it in his mind that the option is there. I call that the friendship phase and I assume he has this for everyone of his friends he made in this manga.
Right now he is at the stage where he can envision or is in the process of envisioning stairs past the pedestal, but for him to do that he would have to stand on the pedestal himself with his partner but that's something extremely unfamiliar to bro and will take a while (another 50-100 chpas idk)
It might not become a threesome because I feel like any one of the three would find it disrespectful if that option was even considered. They worked too hard in their own development to choose a cowardly answer like that. It undermines their progress to a degree and they would feel it











Took me a little bit too long to understand but correct me if I'm wrong
Those flowers actually do hold universes of their own (a personal head-canon of mine is that the planet they're on isn't a planet but a higher dimension) and when mini Phos landed on top of the universe gems, the bigger portion of his structure that broke off got sucked into the gem and turned into that larger comet we see in the second last panel.
Sheesh that took me too long to understand but thats objectively what had happened, but if I had to put in some personal speculation, it mentioned on the last panel that Phos being Phos travels through space and time and shines brightly all the while. it say this right after a Phos lookalike observes the now formed Phos comet. That lookalike being in a giant grassfield much the same as we first see Phos-prime in chapter one and in the same exact position we first see Phos-prime.
I'm not trying to say they're the same Phos (I am cuz cope), but it's clear the author wanted us to draw some parallels. The only thing off about my theory is that the Phos-lookalike observes this comet at night (I think even tho i'm convinced that comet panel happens right before the first panel of chapter 1), and Phos wasn't allowed out at night.
Yo in my last paragraph I mentioned the Phos-lookalike observed the comet at night, but nah cuz the panel says "I hope they can brighten up someone's day."
Keyword being Day so its very plausible thats the same Phos and I'll tell you why. In chapter 1 Phos wakes up from the grass and gets up in the same position we see the chapter 108's second last panel. After that, he pumps himself up to go and finally ask to be a front liner on the field and fight.
My head-canon is, he was feeling a little depressed about being useless so he went to the field to clear his mind and then sees a comet. After observing that comet, he feels better as the chapter 108 panel suggests and gets the courage to strive for his goals.
Phos always had the tendency to break, but it in his nature that despite that shortcoming, he always wanted everyone to smile and be together and also despite that same shortcoming he still got up again to try another time. Its just that along the way he lost sight of everything and eventually became human but that nature stayed the same till the end.
Its very symbolic in the last chapter because mini-phos breaks due to his curiosity and splits in two but despite that, he other half turns into a comet that now strives to make others smile despite being broken himself. Its crazy cuz mini-phos shouldn't have memories of being his human self and yet still that nature.
Its like despite all the tragedies he had faced, he still decided to give courage to his past self to get up and try and that everything will be fine in the end.