Jin was shocked to not find Nes in her bedroom. He looked for her all around the mansion, but she was nowhere. Then again, he looked everywhere except for Seth's office and bedroom. If he was right, Nes was in Seth's bedroom, doing something Jin clearly told her not to.
Jin was not someone to be involved in his friend's sex life. However, could she not listen to him just this once? If it was someone else, Jin would not mind. However, it was Seth; he was someone Jin was not sure they should trust.
He went to Nes's room, got his pillows, and went back to his own room. There was no point in sleeping in her room anymore. She had done it anyway. If it was a normal time, even then he would not mind her being with Seth. But now, it was a time when they should not trust anyone. Seth was doing something to Nes. He could not doubt his suspicion anymore. Nes was not like this after all. Nes would not make such abrupt decisions.