Yes, thanks, it has English too. This looks like an old fork of Boltz frontend, before chain swaps were added. But there is no direct link to repo, so hard to say what code it is actually running.

The fees are identical to Boltz's, so they might just be using their backend to earn rebates. No benefit for the end user, except maybe Japanese language which we can easily add to our site.

And the idea is really to have all such implementations in one place, so they are easier to find and compare the fees.