Japanese flick input is closer to thumb-key ( https://github.com/dessalines/thumb-key I just discovered in another comment), and even that's a bit different as you get to input a consonant+vowel pair at a time (e.g. ka-ki-ku-ke-ko on a key)

I switch between Japanese input and hacker keyboard all the time for termux and it's much faster to type Japanese; this thread made me want to try both thumb-key and unexpected keyboard but I think I'll try thumb-key first.