Not parasite being how Ivan yearns to essentially be carved into till to the point they are inseparable. His perspective of himself being that he is nothing more than a parasite that people don’t want to be around and Till is the light and to him is perfect- Till is his paradise and Ivan somehow wishes that he could live in Till. He doesn’t care about Till’s confused gaze because it’s on him and that’s all that matters. He wants to take the two pieces of messed up flesh and put them into one, a disgusting array of devotion, love, and beauty.
Also notice how this is the first time someone has ever mentioned a full name of another song in their solo- It’s supposed to be about Ivan but his entire solo is dedicated to Till. Just like his entire existence and death. It was all for Till.