“Rightfully” is the opening them of the Anime “Goblin Slayer!” which is based on the Light-Novel of the same name by Japanese author Kumo Kagyu (蝸牛 くも)
The song can be seen through Goblin Slayer perspective as the Goblins have taken everything away from him. his village and family as they were important to him and he doesn’t want the same fate to fall upon other people so Goblin Slayer whole life has been based on exterminating the Goblin race due to this and the trauma of seeing his sister gruesomely violated and killed by the Goblins.

Even though the Goblins may be small and somewhat dumb…they aren’t COMPLETELY ignorant and are very crafty creatures.

Heroes and Adventurers would rather go clam the fame of slaying the Demon King rather than handling a problem that will steady grow at a alarming rate and will soon be out of their control. they would rather devote their focus to the big problems first which is slaying the Demon King rather them the Goblins. they might say the Goblins are little bugs that you can squash with their boot but in actuality they are terrified of the goblins themselves as much as a normal person (mostly the female Adventures) but Goblin Slayer doesn’t care as to him it NEEDS to be done

To reclaim what is rightfully yours which Goblin does at any cost. he wants revenge and he shows no mercy to ANY Goblin as he doesn’t believes creatures like the Goblins deserve to exist or can change as to him the only good Goblins are the one that don’t come out of hiding.

The Pre-Chorus shows his endless fight with not only against the Goblins but the Gods who would sit by and do nothing but play with Goblin Slayer life as the “die gets rolled” they are with each time Goblin Slayer fight goblins are some what lowering the chance he’ll live which is upping the stacks for Goblin Slayer much to their joy. meaning Goblin Slayer has to try MUCH harder then before but the more he struggles and overcome these obstacles, the more the sadistic Truth and Illusion are just gonna keep playing their sick game with Goblin slayer in the middle of it because he makes the “game” much more fun and intriguing so they’ll find a way to force him into a corner by putting the odds with against Goblin Slayer as when they “roll their die” fate is by that point set in stone for the Adventures along with Goblin Slayer but unbeknownst to him his determination and undying thirst for revenge are the only things that can stop Truth and Illusion from getting what they want .