As far as I can tell, the English rule is "sometimes we take the loanword's pluralisation, sometimes we don't, just memorise every single case and don't worry if you get it wrong sometimes"

For example, Samurai and Kimono are both loan words - but we import the pluralisation of Samurai (Seven Samurai) [1] whereas Kimono pluralises with an s on the end (Seven Kimonos) [2].

[1] https://www.merriam-webster.com/dictionary/samurai [2] https://www.merriam-webster.com/dictionary/kimono