World has dungeons that one day popped up and is killing everyone. Armies start sending hunters to go fight, but it still isn't strong enough. Hunters surviving is low, but can protect and exempt other family members from joining the army. Uke was adopted and became a hunter so seme doesn't have to go to military service, wants to protect his seme younger brother. Seme likes uke but upset that he is deployed to hunter dungeons. Uke gets stuck in a time dungeon for 10 years. Seme saw him go in and ends up becoming a hunter to so that he can save uke.
The Hunter's one night