One inconsequential headcanon I cling to is that all the cat rangers purr
Genba purrs constantly but it's soft and light so it's hard to hear unless you're right up in his business (if you subscribe to Genba being more fox than cat, foxes also purr fun fact)
Eiji loud as fuck purr, not too dissimilar from a car engine. loudest when he has a tummy full of raw veggies
Akira insists that he doesn't purr but Kagura SWEARS she heard him do it once. he does purr it’s just rare. very low pitch, very cute (according to Kagura)
Jan is not literally a cat and tigers can't purr, but he makes so many sounds in canon anyways so why not have him make mock purr sounds when he's happy. if you touch him when he isn’t expecting it, he does the lil activation noise too. you know. mrrp?