Is one of the stupidest mechanics in the game. you literally cannot just afk farm on him if you wish like you can on literally ANY other jungle champ...you MUST gank in order to fill your meter...and not just a little bit either...I've found it usually takes about 4-5 ganks to fill that damn thing. I should take less fighting to fill it first of all.
Secondly, to make matters worse you have to pick and choose your targets to fill it with the right color. Now...maybe this wouldn't be a big deal, but the big deal is that the runes used for blue Kayn and red Kayn are different...so it's not really a choice you make on the fly in game, it's something you've already chosen before the game even begins...so you're basically pigeon-holed into only ganking for certain lanes in order to fill the meter with a certain color...because you need to get the form that matches your runes.
Character would be much better if you didn't have to fight so much to fill the meter, then once full got to choose whichever form you wanted.