Gonna be my longest shot for sure, but here goes. 1.) Shouldn’t be a reincarnation/other world transfer fantasy, should include war/kingdom/senki-like elements though. 2.) Was a manga adaptation of a novel, manga was fan-TLed before 2014, and according to those in the know, ended right before “getting to the dark stuff” of said novel. 3.) Cunning/mostly-all-talk MC, with himekishi-styled heroine that is more mature than hime. She’s not the only character from that archetype, and he is not a demon king. 4.) They met as she was... invading his castle? She was following instructions from someone else? He was left behind or advised against staying, but waited for her anyway in the throneroom, and then proceeded to bargain with her after she blew the roof off the castle (serious scene)? They work out a contract where she doesn’t kill him cause it goes against her logic, beliefs, n blah? There’s a window jumping scene somewhere later, my memory fails me. 5.) ???? 6.) 90% sure JP, could be KR, most likely not CN.