Imagine petting kitty!Genji and he tries to hold back the urge to purr. The noise that comes out of his mouth is like a strangled screech but the rumble in his throat is already starting.
He tries to make it sound more like a growl to appear tough and he get real fussy, trying to move just out of your reach so you’ll stop scratching all his good spots.
But it soon becomes too much and he succumbs to the pleasure. He melts into your touch and starts to quiet down, leaving only his gentle purring to be heard.