It's Achi thinking his body is tofu.
It's him believing he is ugly.
It's him wanting to hide so he doesn't have to be in the same vicinity as perfect-body Karan because he feels disgusting.
Only for him to accidentally bump into Karan while trying to leave and realizing that Mr. Perfect Body cannot open his eyes because he will stare lustfully at Achi.
It's hearing that Karan has to meditate next to his naked body, so he doesn't look at Achi disrespectfully.
Karan is not cool-as-a-cucumber here but instead trying to chill the fuck out, so he doesn't act on his impulses.
This one minute scene isn't just about how Achi sees himself but how he believes others see him. Karan has only been a kind and sweet man to Achi and all his coworkers even before Achi could hear his thoughts, yet Achi still expects Karan to be appalled by him. Because Achi has low self-esteem, he, unintentionally, makes Karan the bad guy.
People hate hearing "If you can't love yourself, how in the hell you gonna love somebody else?" because, much like Achi, knowing you are loved helps people love themselves, but the saying rings true since not loving yourself makes you think the worst of others.
The scene isn't about Karan internally freaking the fuck out every second he is near Achi, but about Achi learning his mere presence is capable of eliciting such a response.
Because Achi has to learn to love himself first.