Grimworld[]
(死神界（グリムワールド） Gurimuwārudo?, lit. "Grim Reaper World") The home of the Grim Reapers, which lies in a different realm.
Grim Reapers[]
(死神 Shinigami?) Individuals that come from Grimworld whose duty is to collect the energy that is no longer needed by dying souls. They also come to the human realm in search for a "Special Specimen". Once they have found the one, they will create a contract with the person so when the person dies, the Grim Reaper well obtain this energy and level up in rank. However, they do not know what happens to the soul or where it goes after the person dies. But in order for a Grim Reaper to be active in the human world, which they consume a lot of energy just by being in the human world, they need to replenish that energy from a human that they make a contract with.
Broken Swords[]
(折れた剣 Oreta-ken?) Powerful legendary swords that have been broken in half to control their destructive energy. If the two halves were to rejoin, it would bring forth total chaos. These halves are given to two household families in Grimworld, and are used to form a contract between a Grim Reaper and his/her human energy source. To form the contract, the Grim Reaper uses the Broken Sword not on the physical body, but on the soul of the human, where it remains while the contract is in place. Once this ritual is performed, it connects both of their souls, and, as such, the Grim Reaper is able to replenish his/her energy from the contracted human. It is said that the hilt is often referred as female and the blade as male.
Gram[]
(折れた剣のグラム Oreta-ken no Guramu?, "Broken-Sword Gram") A sword once owned by the God of War, and now resides as a Broken Sword. The Restall Family hold possession over the hilt-half of the Broken Sword, which Lisara uses to form the contract with Ryosuke. The other half of the Broken Sword, the blade half, was possessed by the Galdarblog Family, but unfortunately it was said to be lost. However, later it is revealed that it was inside Ryosuke, thus giving him the full power of the sword (with certain risks). Ryosuke's father was a member of the Galdarblog Family, and was the one responsible for putting the blade half (the other half of the Gram sword) in Ryosuke while he was in his mother's womb.
Singular Person[]
(特異者 Tokuisha?) A special specimen. Only a few exist in the human world. These people are the ones that end up becoming heroes or famous people with famous talents, like painting or writing novels, someone with greatness that they process lots of energy due to his/her passion. Once they die, that energy can be used by a Grim Reaper to level up in rank.
Energy[]
(エナジー Enajī?) All the souls of living organisms are connected to their body by energy. Grim Reapers use this energy to remain in the human world and level up in rank, making their family also more powerful in status.