okay spoiler time, based on novel honestly not much happen, that scar guy is Philip's nephew and he comes over or starts blaming Sahan on phone. Asks if Sahan understands why Philp killed himself now that he was back on earth safe and Sahan says he doesn't know.
after that Heegeon blames himself as well for asking Sahan not to go but Sahan explains that while he can't be 100% sure but if he and Philip both were thinking the same it was because after spending 1 year in space when they came back they felt like they were in the future. They saw that even if they dissappeared for 10 whole years in other people's lives everything and everyone moved on, which made their comeback out of place like they have become outsiders in their own lives.
Philip while he was in space would share with sahan about his beloved little nephew who needed a skin transplant after a bad burn on this face. The whole time he was in space he would say how much he wanted to go back to earth so he could have been the donor and help the little boy recover but now when he actually came back, he saw that boy grow up, recover and still live a good life, saw that in which way he thought he was useful actually wasn't needed and fell into despair and depression, lost the purpose in living.
listening this Heegeon got scared and assumed that Sahan also felt same way but living and dying but Sahan reassures him that at least for now he doesn't feel that way, that he wasn't that attached to his 'life purpose' that much anyway but he too felt somewhat lost.
Honestly there are more details in novel but it finishes somewhat open, they stay together, Philp's death doesn't really shake their relationship that much nor does Sahan fall into depression or self-blaming. Heegeon just asks Sahan to spend rest of his days that he's willing to live with him even if it's not forever.
Can a kind soul spoil me