This story is set in a fictional Korean Empire unrelated to actual history. 'Hoeun,' the youngest master of a prominent noble family in the Korean Empire, is always ill. He goes to the hospital for a bout of body aches, and the doctor tells him an unexpected story. "It seems that Master Hoeun... has become an In (Guide)." "What you're suffering from isn't body aches, but a manifestation pain." Hoeun, who has grown up like a precious flower inside the walls of his house his whole life, is excited even though he has to go to the battlefield right away. He participates in the matchmaking event to find a Gunsin (Esper). There, Hoeun meets 'Taemuk,' the strongest Gunsin in the Korean Empire, and they become partners. Unlike Hoeun, who is excited to have someone to spend his life with, Taemuk is aloof. He has no interest in Hoeun and only desires his body. "General, please reconsider..." "Shit, yesterday it was this, today it's that. Why did you even come if you're going to be like this?" "..." "You seem to think you're still a noble young master here, but don't be mistaken. You're just my In." "..." "Do as you're told. That's your job." "If you say it's my job..." "You have to strip and hug me. As vulgar as possible." What will happen to the two of them in the middle of a battlefield swarming with cannibalistic monsters?