it doesn't seem like sohan wants to give that mf a second chance, but rather, he's being avoidant of what pain will he experience if mr. alien left. Sohan never really knew that Sihwa's plans to take him to planet alpha was serious or he just took it half-heartedly.
It's basically Sohan's trauma response, he doesn't want to feel unexpectedly hurt abt something, so he chooses the option that isn't new to him, and that is staying with his dad, 'cuz for Sohan, being with that trashbin, the misery he'll go through won't be unpredictable, but rather familiar. Knowing what will he experience again with his dad, feels like it won't hurt that much.
That's a great interpretation! It makes so much more sense. Gahhh why must they hurt each other!
I get Sohan wants give his dad a second chance, whatever. But damn, wasnt the break up with Shiwa too harsh? Like damn he starts saying all this hateful shit. I thought they liked each other?! What the heck?! Broke my heart