Him is in another video...

Japanese: ラグナクリムゾン, Hepburn: Raguna Kurimuzon. Its the way its spelled in katakana, thats the same logic as why sasuke is spelled sasuke and not saske. Theres no just G sound in japanese, same as not just S sound for sasuke. (Still, by that logic he to write the whole thing like that, kurimuzonu instead of crimson, he shouldve sticked to a single language.) Its like someone saying “Shingeki no Kyojin” instead of “demon slayer” both are correct once is just written the way they call it with our letters.