Tangu

Thanos lived with his mother in Seoul. By the time summer arrived, Thanos had already made his summer plans. But they were dashed by his mother's words.
— Son, do you remember Nam Gyu? Well... We're going to Busan today for the whole summer. And we'll be staying with my friend... (Nam Gyu is my mother's friend's son.)
Thanos immediately frowned, clearly showing his displeasure.

Explanation:
Thanos knows Nam Gyu. They met when they were five, then seven. Nam Gyu was always moody and a whiner. He constantly complained about Thanos, snitched, and exaggerated his actions. If, for example, Thanos simply pushed him, Gyu might make up that Thanos slapped him and punched him in the stomach.
Usually Thanos was scolded afterwards, and Gyu was given candy.

Thanos, as usual, was packing his things with complete indignation, arguing with his mother, saying:

• Come on, Mom! I don't want to!
  In the end, they barely managed to get ready. Thanos stood disgruntled, leaning against the wall near the door.
  Mom: Son... You will sleep in the same room with Nam Gyu.
  Thanos's face looked as if he'd just been told, "Thanos, you're going to marry Nam Gyu." For him, it was a death sentence. He immediately started yelling and arguing, until his mother threatened to take his phone away for the entire holidays. Well, that calmed him down...

They boarded the plane, and as they flew, Thanos, as usual, cursed everyone and everything. He clearly didn't want to run into that tattletale again.

And so they arrived. There was a knock on the door, and it opened. Mother's friend was standing there. And somewhere nearby stood Nam Gyu. He looked quite handsome. Eventually, they all went to the table, where there was a pile of food. Thanos began to devour the food, as if he hadn't been fed in weeks. Thanos added all sorts of jokes and imprinted his words into the conversation.
Gyu remained defiant and dissatisfied.
Everything was fine until they were given the cake and told to divide it. Well, they ended up arguing and fighting because Thanos, in Nam Gyu's opinion, had cut off two millimeters too much for himself. Now they were sitting (each with a black eye, and Thanos with scratches) leaning on each other's backs.