I am looking for something that could work with Asciinema, but honestly, anything that works at this point even if I had to change screen recording tools would do the job.
Just a side-note, though that doesn’t help, sorry.
Asciinema already allows recording your keystrokes since v2 and they are part of the recorded file.
However, the player cannot show them, yet: Key-press overlay · Issue #152 · asciinema/discussions · GitHub
Anyways, looking forward to Kakoume recordings by you that include keys 
https://www.thregr.org/~wavexx/software/screenkey/ is often used with regular screen capture tools.
Thanks for the tips!