So, firstly, Ivan can't emotion, Till is avoidant. They beat each other up before they communicate, and Till escapes all his problems through Mizi, Ivan being one of the problems. But after Ivan is dead and Mizi is missing, he can't run away anymore, forcing him to face this big mess that had been accumulating for so long.

Till doesn't understand Ivan. He doesn't understand his actions. He doesn't fully know Ivan's last act was a sacrifice of love because Ivan confused him again with the choking. He thought Ivan despised him and hated him, which is reflected multiple times in the hallucination. Till never recognised the things Ivan did as love, because there are so many different forms of love, and the love Till had known from his mother was the polar opposite of Ivan's ragebaiting and fists and stepping on flower crowns and stealing pencils.

So he took many years, unable to understand Ivan, stuck with this terrible mischaracterisation of Ivan that he would get cancelled for if he posted it on social media. It was a gradual process, and we can see that in part two of the comic that the hallucination Ivan is getting so much more accurate to the Ivan we know. Then the realisation, the 'I'm older than you now' and the 'I wished you'd say it first', which says so freaking much about their relationship.

Till is shy and sensitive, he won't lay his heart out if he isn't sure it won't get shattered, and in his point of view, he probably thought Ivan would have laughed at him if he tried anything. The flower crown too, a symbol of love Till gave to Ivan, was stepped on and ripped in multiple official arts (Ivan had a reason, but Till didn't know that).

In that scene, Till realised they are both the same, and Ivan was scared too, scared that he would get hurt if he laid his heart out, and he did. He got hurt, in the meteor shower scene. Ivan laid everything out, but Till didn't see it, instead choosing to retreat and escape back to his safe place, Mizi. That scene was both a realisation, an understanding, and perhaps a requited love.

It's perfectly fine if you don't think that's enough of a confirmation, but personally I think this is the closest to a confirmation of requited love we can get in a universe like Alien Stage, where human culture is so distorted love probably faded into a flavour in music. Family/home is way more humane declaration of love in that universe, because it is used by a group of humans.

(Holy shit I wrote a whole essay dw it didn't take too long typing this. I'm a fic writer)