It seems that 矢志不渝 [1] is a more close analogue in that this exact four-letter form is always used. The Korean version is substantially different too, it's 初志一貫 (초지일관 Chojiilgwan).
As a Chinese person, I perceive "初志" as having a connotation of "original" or "initial" intentions, whereas "矢志" simply implies determined wishes or promises without emphasizing the "initial" aspect. While I'm not an expert in Japanese, my understanding is based on the Chinese perspective, and the actual meaning in Japanese might differ. It's intriguing to see how these nuances can vary across languages and cultures.
I personally analyze 初志一貫 as simply being consistent (一貫) from the beginning (初志), not necessarily retaining the original subject (only implied). I believe this is the most frequent Korean interpretation because 初志 초지 is not a common Korean word (its synonym 初心 초심 is common) and 初志一貫 is probably the only phrase you can find this word.
[1] https://baike.baidu.com/item/%E7%9F%A2%E5%BF%97%E4%B8%8D%E6%...