The most painful part of Kan and Thua is that they both want the exact same thing. They want to hold hands, they want to smile, they want to laugh, they want a chance to be be themselves together. But Kan is terrified of the judgement he sees cast and Thua would rather disappear then face people alone. They both ache and they both hide and the silence when Thua lets go of Kan's hand because Kan has frozen in the moment shakes the rest of the episode.
Because that is the moment of realization for both of them, a moment when Kan knows he is a coward and Thua knows he isn't going to fight and they both have to admit to themselves who they are and who the other is. That Kan must see that he is not the knight he wants to be and Thua knows he is fighting alone.
Kan is so happy to grab Thua's hand, to guide him to safety, to protect him from the threats he perceives... but the threats he sees are not the real danger. The real danger is his fear, the real danger is him.
Thua wants, needs, someone beside him. He needs to be supported, he needs to know he's not alone and while he wants Kan to support him... Kan can't. Kan is a coward, Kan freezes, Kan cannot stand alongside Thua. He can stand behind, he can punch someone in a bathroom, he can stand on a beach and promise to listen.
But he is not strong enough to face them head on, to face the judgement that Thua faces every day.
Kan hates himself for being queer, Thua hates himself for being silent.
A coward and a bystander fall in love and they disappoint themselves again and again, hurt themselves again and again, stare at each other with longing and pain but knowing that they are not good enough for what they want, hating themselves and cursing themselves, Thua wanting to disappear and Kan wanting to do so much he can't.
Their relationship is going to hurt so much because they're both struggling so much just within themselves. Thua has closed himself off and Kan protects himself with anger and jokes and when they're alone together is when they're most honest about who they are but that just isn't viable for either of them.