What gets me about Labru is Kabru dragging himself through nine circles of hell just to fall at Laios's feet and say you, I want you. It's Laios, who has always felt unwanted, out of step with humanity, confronted with a man telling him On purpose, I want to be your friend on purpose, not accidentally. I have every reason to hate you just like all the others who rejected you but I want to know you more instead. It's about the ways Laios says to Kabru, who does not eat unless he's choking it down, Let me feed you.
It's all the secret things about each other that neither of them know yet, but could. It's about the loneliness, the thirst for knowledge, the lifetimes of othering. It's about having your head in the clouds and your feet on the ground, a clear view of the horizon and a body rooted to the earth. It's the ways they both hunger and are afraid of hunger. It's about what it would mean for Kabru to desire a man who wants to be the thing he fears most. It's about Kabru wanting Laios to understand him the way he understands monsters (Laios eats monsters). It's about what it would mean for Laios to want Kabru, human to human.
so much of all this but @yuri-puppies tags really nails that Kabru... wants to heal. He hates monsters but used to othered for being seen as one. And when we see them meet we expect a disaster to happen, but Kabru is wiser than that to the pitfalls of alienation. He sees what Laios' love for monsters allows him to do (that's obvious to the audience, but on the first chapters we see Marcille&Chilchuck surprised that his knowledge is useful to them).
That's why the same way we see Laios consume monsters and take them down from the pedestal of incomprehension and thus taming into knowledge... We see Kabru do to humans, specifically Laios. Kabru runs himself to the ground for his objectives, and eliminates threats both in monsters and humans. But after meeting Laios he connects to his philosophy (talks about the dungeon's "nutrition" to convince the canaries), is equipped to care for Mithrun by the knowledge shared, avoids monsters instead of fighting head-on, is not hostile to the Touden party even after catching them trying to hide the winged lion. I see a beautiful future.