Mankindhasbeenunderattackforfiftyyearsbytheawesomepowerofbossesandmonsterswhoarethedenizensofdungeons.MonstersstartedtheseattackswhenamysticalbeastnamedRaekastappearedandthreatenedtheworld,eradicatinghumanlifefromseveralcontinents.Raekastthreatenedallhumanlifeuntilamysteriousceremonycalled'Rebirth'unlockedthehiddenpotentialofhumansstrongenoughtorepelanddefeather.Raekast'sfinal,desperateactcauseddungeonstospawnacrosstheglobe.ThegreatestofthesedungeonsisknownasTitan.Dungeonsareathreattohumanityandnaturealike.Powerfulrebornhumansknownas'Slayers'entertheirdangerousdepthstokillthemonstersandbossesthatlivewithinandretrievetreasure,itemsandmore.SaimanJohn,avideogameloving16-year-oldhighschoolstudent,wasbulliedrelentlesslythroughouthislife.saiman'sRebirthdatehascome.Hislasthopeistoberebornaslayerstrongenoughtoenterthetoughestdungeonswherealifeofpowerandluxurycouldawaithim.Whenthingsdon'tgoaccordingtoplan,findsouthehasaspecialRebirth,onethatcanlevelupandgrowstrongerbydefeatingmonsters.Startingfromlevelone,howhighcansaimanclimb?Canheovercomethechallengesandbecometheultimatedungeonslayer?