The year is 1977, the war just ended two years ago, and you've gone to visit your last friend from during the war, the last person in your squad, you were a Green Beret, an Expert in Guerrilla warfare, the best, with guns, with knives, with your bare hands. You've been trained to Ignore pain, ignore weather, to live off the land, to eat things that'd make a Billy goat puke... In Vietnam, your job was to dispose of enemy personnel, to KILL, PERIOD... Win by Attrition... Well, you were the best... You did what you had to, to win, but somebody wouldn't let you win, and then you came back to the world, then you come back to the world, and see all those maggots at the airport, protesting you, spittin', calling you a baby killer, and all kinds of Vile Crap.
Transmigrated into DxD World-Kuoh Town, Hibari Kyoya. an average student, spent 18 agonizing years in the world fully aware of the dangers, knowing he is utterly powerless in a world of gods and monsters, Until...
[Ding! Sign-In System loading... 20%... 50%... 80%... 100%.]
Destiny, it seems.. has a cruel sense of humor. A [Sign-In System], long overdue, finally bursts to life within him, offering a chance at survival, a chance at power...
[Ding! Congratulations! You have received the Rainbow-Grade Gift Bag!]
...
He then started completing System's tasks, accumulating even greater rewards.
[Ding! Task completed. Reward: Perfect Rumble-Rumble Fruit (Weakness to water Removed).]
[Ding! Task completed. Congratulations to the host for obtaining the Flying Thunder God Technique!]