You say that all of the universities you've emailed "mentioned repeating first year". Does that suggest that you're trying to switch
subject? Or that the way your course is taught in Japan in very different from the way that same course is taught in the UK? It could just as easily be that UK admissions tutors aren't terribly familiar with the way your course is taught in Japan and so have no reasonable way to evaluate whether what you've covered so far is equivalent to what you would have covered at their own university. Did any of them ask for you academic transcripts or details of what modules you'd covered so far?
I just did a quick search to establish whether UK universities typically have processes in place for international transfers. The first relevant hit was
this one from University of Gloucestershire, where they say: "We have agreements in place with a number of partners worldwide, which allow students to progress their education on one of our degree programmes. These ‘pathways’ allow entry with advanced standing (coming into the degree programme at an advanced level rather than the beginning) onto specific courses."
This page from the University of Bristol also talks about, "Transferring your studies to the University of Bristol via the Global Transfer Programme provides you with several advantages."
According to
this page, transferring to University of East London wouldn't be possible, as they say, "If students have completed a
2 years of a college/university programme or hold an Associate degree in a relevant subject, with a CGPA of 2.0 they may be considered (at the University's discretion) for advanced entry."
The same is true of King's College London, as they say
here that "Students completing some overseas degrees will be required to have completed a
minimum of two years of study before transferring to King’s College London." (However, note that that say, "some".)
So I think you just need to keep contacting UK universities (and checking the rules on their web sites, as I've done above) to find out if they would consider accepting you as a transfer student.
(By the way, it is not true to say that "UCAS applications are over now and can only apply for 2024 entries". The "equal consideration deadline" was back in January, and today is the last day which universities have to make offer decisions for applications who applied by that date. But there are plenty of course which still have places, and which you can still apply for - to start this September. You just need to filter by "Show courses with vacancies" once you've done your initial UCAS course search,
here.)