If you use Shadow Movement to sneak into houses and a pegasus team to pull the flying sleigh... yes, in this world, it's possible to become Santa Claus! But... the Christmas tradition doesn't even exist in this world. When Rimuru tries to explain it in detail to the people of Tempest, they end up summarizing it as a "party." The Christmas cake and presents are ready, and most importantly, Kaijin and the other Dwarves create gorgeous decorations that bring the Christmas mood to Tempest. On top of that, Eren and the children treat everyone in town with their heavenly singing.
It's because I have them that I can 
feel at ease counseling you about...
...وبفضلهما أشعر بالرّاحة عند استشارتك حول
Nur weil ich sie an meiner Seite habe,
Gracias a ellas
Gracias a ellas
C’est grâce à elles
que je peux papoter avec vous
È proprio perché ho loro al mio fianco 
che non ho alcuna preoccupazione
É só por tê-las comigo
Они для меня надёжное подспорье.