Yes, Romaji is also used by the Japanese language, and the official Romaji for 剣聖 (けんせい) is KENSEI
Standard Japanese vowel sounds are very similar to standard Spanish vowels, if that helps. Just 5 vowels to worry about, AIUEO – Ahhh, Eeee, Oooo, Ehhh, Ohhh.
In this context, Ken means Sword...