• Bayonet - A specific type of weapon that unifies sword and gun. As example Kai's Drake Nail whose body is that of rifle (Mosin-nagant style) with sword's blade integrated into barrel.

  • Code Holder - Magical artifact of unknown origin. Supposedly able to cut anything that threatens life of wielder (most notably magic). jp. 世界座標の鍵 furigana コードホルダー

  • Drake Nail - The model name of Kai's weapon. It is relatively light and can be hold in one hand. Capable to load special bullets that are able to produce effect, similar to that of offensive spells. jp. 亜竜爪; furigana ドレイクネイル

  • Graveyard - jp. 墓所 Name of mysterious black pyramids where four races were sealed away allowing humans to triumph in Kai's original world.

  • Human city - Any city where humans live, in the alternate world where humanity has lost. Often hidden from enemy sight by being underground. jp. 人類特区; furigana ヒユーマンシテイ

  • MDA - jp. 人類庇護庁 - Mankind Defence Agency, organization from Kai's world which had a goal to ensure peace after humanity won in the great war. Militant in its goals, due non-human races being sealed away they had a little to do aside from amassing technologies and training soldiers.

  • Sidhe - jp. 蛮神 - Literally foreign gods. In japanese it is often used to refer to gods of religions that came from outside of Japan (i.e. anything other than Shinto). In novel it refers to alliance of races: elves, angels, dwarves and fairies. Word used here is generally unused outside of context of japanese religion, but author uses it. It is not clear whether elves and their friends came with the term themself, but since they use human language, it is likely that idea would be coming from humans. Due to that I decided to use term Sidhe that was used in irish mythology to refer to fairy folk, but also often referred to super natural creatures in general (e.g. Bean sídhe, Leanan sídhe). 蛮神 seem to be used in similar way to Sidhe as both are super natural creatures and similarly encapsulates various sentient super natural creatures. Pronunciation is akin to Shii despite it being written as Sidhe (i at the end is long).

  • True world - jp. 正史 While technically it mean true history, in scope of the translation it is interpreted as world rather than history making it a more plausible wording. In general it refers to the world from where Kai came from: world where all four non-human races are sealed away in graveyards alongside with Rinne and Code Holder being in demons' graveyard.